Hi everyone, I'm here to present a team I created but I need some feedback and expert advice to strengthen it.
First I have to say that this team was built to play on 3DS, where we play all smogon's rules except that sometimes we play at level 50 for beginners.
It works on Showdown of course but some choices that I made were here because on 3DS there is more hyper offense and less stall team. I hope I'm still in the RMT's rules.
So here we go !!
Teambuilding process :
So first I wanted to play Gengar sweeper hex because this thing hit like a truck, can 2hko a lot of the metagame and I have to start somewhere.
I needed toxic spikes for the synergy, I choose Dragalge for his bulk so he could put the TSpikes in early and mid game twice.
Now that Dragalge is up, I need another stall who could put some hazard and protect my team, ferrothorn was, for me, the obvious choice
Then I knew that dark type and Gengar are great partner, I choose to add M-Gyarados
Here I note that I'm very weak to M-Loppuny and M-Pinsir, to palliate this Talonflamme was a good option
Sets detailed :
Gengar Majax ( Gengar ) @ Life Orb
Ability : Levitate
Nature : Timid
EVs : 4 HP / 252 SpA / 252 Spe
-Hex
-Sludge Bomb
-Will-o-Wisp
-Icy Wind
The beast is here, as I say it's my team's center and my win condition. Gengar is one of the bestversatile sweeper as he can use taunt, trick or sub, but no one is expecting a pure life orb sweeper.
He is here to revenge kill in mid an late game, as he have to wait that some opponent's pokemon are poisoned to do his magic. He can also be a good check to CM M-Sableye since he has 50% to OHKO after rocks and T-Spikes.
Do you know why his nick name is Gengar Majax? Because he is so purely powerfull that he can make disappear the opponent's team just by snaping his fingers. ( If you don't understand , Gérard Majax is one of the most famous French illusionists )
First I have to say that this team was built to play on 3DS, where we play all smogon's rules except that sometimes we play at level 50 for beginners.
It works on Showdown of course but some choices that I made were here because on 3DS there is more hyper offense and less stall team. I hope I'm still in the RMT's rules.
So here we go !!
Teambuilding process :

So first I wanted to play Gengar sweeper hex because this thing hit like a truck, can 2hko a lot of the metagame and I have to start somewhere.

I needed toxic spikes for the synergy, I choose Dragalge for his bulk so he could put the TSpikes in early and mid game twice.

Now that Dragalge is up, I need another stall who could put some hazard and protect my team, ferrothorn was, for me, the obvious choice

Then I knew that dark type and Gengar are great partner, I choose to add M-Gyarados

Here I note that I'm very weak to M-Loppuny and M-Pinsir, to palliate this Talonflamme was a good option

And finaly I needed a stealth rock setter and a spinner, I'm not convinced by this, but I put Donphan in this role.
Sets detailed :

Gengar Majax ( Gengar ) @ Life Orb
Ability : Levitate
Nature : Timid
EVs : 4 HP / 252 SpA / 252 Spe
-Hex
-Sludge Bomb
-Will-o-Wisp
-Icy Wind
The beast is here, as I say it's my team's center and my win condition. Gengar is one of the best
He is here to revenge kill in mid an late game, as he have to wait that some opponent's pokemon are poisoned to do his magic. He can also be a good check to CM M-Sableye since he has 50% to OHKO after rocks and T-Spikes.
Do you know why his nick name is Gengar Majax? Because he is so purely powerfull that he can make disappear the opponent's team just by snaping his fingers. ( If you don't understand , Gérard Majax is one of the most famous French illusionists )
Hex is obvious, sludge bomb over sludge wave for the 30% chance haxx to poison flying type or levitating pokemon like rotom-w or zapdos. Will-o-wisp again to pair with hex and for the utility. Icy wind is a little surprise for scarf user or M-Loppuny who would have the great idea to swith-in on Gengar to take 0 damage on Hex, but then you're like " U w8 m8 ? Switch this rabbit in front of THE SHADOW HIMSELF ?? Take cold air to slow down, what you want again? A lil bit of BURN TO TURN YOU IN ASHES MOUAHAHAHAHAHA.
Kulavalechu ( Dragalge ) @ Black Sludge
Ability : Adaptability
Nature : Calm
Evs : 248 HP / 224 SpD / 36 Spe
-Draco Meteor
-Sludge Bomb
-Scald
-Toxic Spikes
I decide to use dragalge over Tentacruel or other TSpikes user because of his wonderfull special bulk. He can came as a lead ( as long as there is no Lando-T or TankChomp lead ), set up one or two layer(s) of T-spike(s) and he can do it again if the opponent find a way to take them off.
Furthermore, he act as a great check to a lot of threat like Charizard-Y, Clefable, Keldeo, Serperior, M-Manetric etc... Forcing them to switch out, FLY YOU FOOLS
Draco Meteor over dragon pulse for more power and can act like an emergency button, Sludge bomb like Gengar for 30% chance to poison flying type, Scald is always usefull in a team and again it's a great statut for Gengar as it can burn steel type like Scizor or Skarmory.
36 Speed to speed creep hippodown at lvl 50 ( but 28 is enought at lvl 100 ), the rest are put in HP and Special Defense to increase his bulk.
But he is very weak in the physical plan.
Sapik ( Ferrothorn ) @ Leftovers
Ability : Iron Barbs
Nature : Relaxes
EVs: 252 HP / 168 Def / 88 SpD
-Spikes
-Leech Seed
-Gyro ball
-Protect
Ferrothorn is an excellent physical wall and cover Dragalge's weakness, he resits psychic, dragon, and take pretty well all the EQs. In the other side dragalge resist fighting and fire.
He act as a hazard setter and a stall who can take on every physical sweeper who don't hit in his weakness.
252 HP and 168 Def to avoids the 2HKO from Adamant Life Orb Excadrill after Stealth Rock damage and some special defense for more bulk.
Leech seed protect is the cancer duo to restore about 20 to 40% of your maximum health in 2 turns ( it's depend on the target's maximum health ) while damage 24% of your opponent's Pokemon maximum health.
Gyro ball over Power Whip to beneficiate of ferrothorn's speed, more accuracy and to deal against ice type like Weawile and Kyurem-B or even TTar support.
There is no more to say, it's a common set, very usefull and with his look says " YOOOU SHALL NOT PAAAAAASS ".
Levy a tord ( Gyarados ) @ Gyaradosite
Ability : Intimidate -> Mold Breaker
Nature : Adamant
Evs : 8 HP / 248 Atk / 252 Spe
-Waterfall
-Crunch
-Earthquake
-Dragon Dance
As I say earlier Gengar and Dark type are great partner as Gengar is weak to Psychic, Ghost and Dark, while Gyarados resist all of them and is weak to insect, fairy, fighting, grass and electric
whereas Gengar resist it ( exept eletric ).
To continue with their synergy, Gyarados can switch in Mold Breakr Excadrill scarf, being immune to EQ, intimidate him and set up or RK, he can take care of levitate and steel Pokemon who are not worry about T-Spikes and Hex ( Like Heatran or rotom-W ). And during this time, Gengar can eliminate some physical wall like Toxic Orb Gliscor, Skarmory ( he can 2hko it without statut after rocks damage or burn + hex is a OHKO ) Unaware Clefable and TankChomp.
But Mega Gyarados is a monster just by himself as he can deal tons of damage just with one DD, 2 it's the end of the game GG WP run away bro.
8 HP are here to have 171 HP lvl 50 and 333 lv 100 so you take 1 less damage from rocks ( 0 HP gives you 170 HP at lvl 50 and 331 at lvl 100 so i needed to have both )
Waterfall for stab, EQ to enjoy a delicious OHKO on rotom-w ( again him ) and for coverage, I put Crunch for a secondary stabb and a way to hit bulky psychic type like slowbro cress, or even Lati@s but I'm disappointed, it never really helped me so maybe Taunt for M-Sableye or Ice fang for 4 time weakness would be better, I need advice here...
Talon ( Talonflame ) @ Choice Band
Ability : Gale wing
Nature : Jolly
Evs : 252 Atk / 4 Def / 252 Spe
-Brave Bird
-Flare Blitz
-U-turn
-Steel wing
Now I know that I'm weak to M-Loppony, Close Combat + SD M-Pinsir, mach punch users and I might have some trouble against chesnaught, so the bird is here. He has a very good synergy with Mega Gyarados, covering up each others weaknesses. He can kill all mach punch user, serperior and chesnaught. He also acts as a back up and third sweeper for my team in case Gyarados's Sweep is not possible due to a threat or has been attempted but failed in mid game or if Gengar can't come on the battle-field. He also can clean up in late game when opponent's team is weakened and he gives me a priority that I was lacking.
Brave Bird and flare blitz Obviously for stab, U-Turn for scout and Steel wing for rock type like Mega Diancie.
Jolly nature to outspeed raikou and OHKO it with flare blitz after rocks ( Raikou is a popular Pokemon on 3DS ).
I don't recommend it because it need so many skill to play it, decision are really hard : will I brave bird ? Or should I Brave Bird? Aaah but Brave Bird is a nice option too... Be careful when using it.
Donphan @ Leftovers
Ability : Sturdy
Nature : Impish
EVs : 252 HP / 4 Atk / 252 Def
-Earthquake
-Stealth Rock
-Rapid Spin
-Knock Off
So there we are... I took this final decision after a long time and a lot of test and I had no choice to take Donphan as my rock setter and spinner.
I don't like regroup those roles because they are so important that if you lose just this pokemon you can not have your rocks up or deny opponent's entry hazard.
Earthquake is the most reliable STAB attack, stealth rock + rapid spin for support, and knock off for utility.
I don't have a lot to say about it, he wasn't useless but i know I can find better.
Threat List :
Mega Charizard-Y, this thing is OP againt my team I only have Dragalge for it and if he packed EQ he can 2HKO Dragalge.
Exactly like Zard-Y, it checks all my team members except Dragalge
Unusual in OU but with is coverage he can gives me a lot of trouble.
Finaly this team is pretty fun to play and very competitive as I used it for somes match and I had a good ratio Win/Loose.
As I said, it was built to play on 3DS so I don't have Showdown replay for you but if you want to you can watch a tournament that I did a few month ago, it was ofc smogon's rules :
Quater final : HQSW-WWWW-WW2R-AGD7
Semi final : PKCW-WWWW-WW2R-AGYS
Final : 3YRG-WWWW-WW2R-AGP3 ( Check it out, that's a good match )
Here is the end of this first RMT, I'm pretty sure you can improve it I trust your powerfullnessy.
I hope you enjoyed reading it, sorry for my bad English and HAVE A NICE DAY

Kulavalechu ( Dragalge ) @ Black Sludge
Ability : Adaptability
Nature : Calm
Evs : 248 HP / 224 SpD / 36 Spe
-Draco Meteor
-Sludge Bomb
-Scald
-Toxic Spikes
I decide to use dragalge over Tentacruel or other TSpikes user because of his wonderfull special bulk. He can came as a lead ( as long as there is no Lando-T or TankChomp lead ), set up one or two layer(s) of T-spike(s) and he can do it again if the opponent find a way to take them off.
Furthermore, he act as a great check to a lot of threat like Charizard-Y, Clefable, Keldeo, Serperior, M-Manetric etc... Forcing them to switch out, FLY YOU FOOLS
Draco Meteor over dragon pulse for more power and can act like an emergency button, Sludge bomb like Gengar for 30% chance to poison flying type, Scald is always usefull in a team and again it's a great statut for Gengar as it can burn steel type like Scizor or Skarmory.
36 Speed to speed creep hippodown at lvl 50 ( but 28 is enought at lvl 100 ), the rest are put in HP and Special Defense to increase his bulk.
But he is very weak in the physical plan.

Sapik ( Ferrothorn ) @ Leftovers
Ability : Iron Barbs
Nature : Relaxes
EVs: 252 HP / 168 Def / 88 SpD
-Spikes
-Leech Seed
-Gyro ball
-Protect
Ferrothorn is an excellent physical wall and cover Dragalge's weakness, he resits psychic, dragon, and take pretty well all the EQs. In the other side dragalge resist fighting and fire.
He act as a hazard setter and a stall who can take on every physical sweeper who don't hit in his weakness.
252 HP and 168 Def to avoids the 2HKO from Adamant Life Orb Excadrill after Stealth Rock damage and some special defense for more bulk.
Leech seed protect is the cancer duo to restore about 20 to 40% of your maximum health in 2 turns ( it's depend on the target's maximum health ) while damage 24% of your opponent's Pokemon maximum health.
Gyro ball over Power Whip to beneficiate of ferrothorn's speed, more accuracy and to deal against ice type like Weawile and Kyurem-B or even TTar support.
There is no more to say, it's a common set, very usefull and with his look says " YOOOU SHALL NOT PAAAAAASS ".

Levy a tord ( Gyarados ) @ Gyaradosite
Ability : Intimidate -> Mold Breaker
Nature : Adamant
Evs : 8 HP / 248 Atk / 252 Spe
-Waterfall
-Crunch
-Earthquake
-Dragon Dance
As I say earlier Gengar and Dark type are great partner as Gengar is weak to Psychic, Ghost and Dark, while Gyarados resist all of them and is weak to insect, fairy, fighting, grass and electric
whereas Gengar resist it ( exept eletric ).
To continue with their synergy, Gyarados can switch in Mold Breakr Excadrill scarf, being immune to EQ, intimidate him and set up or RK, he can take care of levitate and steel Pokemon who are not worry about T-Spikes and Hex ( Like Heatran or rotom-W ). And during this time, Gengar can eliminate some physical wall like Toxic Orb Gliscor, Skarmory ( he can 2hko it without statut after rocks damage or burn + hex is a OHKO ) Unaware Clefable and TankChomp.
But Mega Gyarados is a monster just by himself as he can deal tons of damage just with one DD, 2 it's the end of the game GG WP run away bro.
8 HP are here to have 171 HP lvl 50 and 333 lv 100 so you take 1 less damage from rocks ( 0 HP gives you 170 HP at lvl 50 and 331 at lvl 100 so i needed to have both )
Waterfall for stab, EQ to enjoy a delicious OHKO on rotom-w ( again him ) and for coverage, I put Crunch for a secondary stabb and a way to hit bulky psychic type like slowbro cress, or even Lati@s but I'm disappointed, it never really helped me so maybe Taunt for M-Sableye or Ice fang for 4 time weakness would be better, I need advice here...

Talon ( Talonflame ) @ Choice Band
Ability : Gale wing
Nature : Jolly
Evs : 252 Atk / 4 Def / 252 Spe
-Brave Bird
-Flare Blitz
-U-turn
-Steel wing
Now I know that I'm weak to M-Loppony, Close Combat + SD M-Pinsir, mach punch users and I might have some trouble against chesnaught, so the bird is here. He has a very good synergy with Mega Gyarados, covering up each others weaknesses. He can kill all mach punch user, serperior and chesnaught. He also acts as a back up and third sweeper for my team in case Gyarados's Sweep is not possible due to a threat or has been attempted but failed in mid game or if Gengar can't come on the battle-field. He also can clean up in late game when opponent's team is weakened and he gives me a priority that I was lacking.
Brave Bird and flare blitz Obviously for stab, U-Turn for scout and Steel wing for rock type like Mega Diancie.
Jolly nature to outspeed raikou and OHKO it with flare blitz after rocks ( Raikou is a popular Pokemon on 3DS ).
I don't recommend it because it need so many skill to play it, decision are really hard : will I brave bird ? Or should I Brave Bird? Aaah but Brave Bird is a nice option too... Be careful when using it.

Donphan @ Leftovers
Ability : Sturdy
Nature : Impish
EVs : 252 HP / 4 Atk / 252 Def
-Earthquake
-Stealth Rock
-Rapid Spin
-Knock Off
So there we are... I took this final decision after a long time and a lot of test and I had no choice to take Donphan as my rock setter and spinner.
I don't like regroup those roles because they are so important that if you lose just this pokemon you can not have your rocks up or deny opponent's entry hazard.
Earthquake is the most reliable STAB attack, stealth rock + rapid spin for support, and knock off for utility.
I don't have a lot to say about it, he wasn't useless but i know I can find better.
Threat List :

Mega Charizard-Y, this thing is OP againt my team I only have Dragalge for it and if he packed EQ he can 2HKO Dragalge.

Exactly like Zard-Y, it checks all my team members except Dragalge

Unusual in OU but with is coverage he can gives me a lot of trouble.
Finaly this team is pretty fun to play and very competitive as I used it for somes match and I had a good ratio Win/Loose.
As I said, it was built to play on 3DS so I don't have Showdown replay for you but if you want to you can watch a tournament that I did a few month ago, it was ofc smogon's rules :
Quater final : HQSW-WWWW-WW2R-AGD7
Semi final : PKCW-WWWW-WW2R-AGYS
Final : 3YRG-WWWW-WW2R-AGP3 ( Check it out, that's a good match )
Here is the end of this first RMT, I'm pretty sure you can improve it I trust your powerfullnessy.
I hope you enjoyed reading it, sorry for my bad English and HAVE A NICE DAY