First off, thanks to Blue Kirby for being so patient and helping me get registered! So here comes my first post and first RMT. The main strategy for this team is to trap and faint opponent's pokemon early to mid game when the opponent doesn't know I have these trappers. Main targets include steel walls (e.g. Skarmory, Bronzong, Forretress), counters to my Gyarados & Scizor (e.g. Jolteon, Electirive, Infernape, Heatran), spinners (e.g. Starmie, Tentracruel), and 252 HP / 252 Atk Scizor which are so popular at the moment. Finally when the walls and counters are out of the way I will attempt to sweep with DD Gyarados or SD Scizor! Of course it doesn’t always work like I want it to... and there are some pokemons (e.g. Swampert) or strategies (e.g. rain) that I have no way of dealing with at the moment, and I’m sure I haven’t exhausted the list of things that I’m weak to (>.<), so I'd really need some help. Thank you so much for reading and providing advice!
Edit: Bolded words are changes that I've made according to everyone's helful suggestions. I've learnt so much, not just for this team, but in terms of what needs to be considered when team building. Thank you all!
Note: Latest changes are made after considering suggestions up to Bogmire's post.
Blissey @ Leftovers
Calm / Natural Cure
6 HP / 252 Def / 252 SpD
~ Wish
~ Protect
~ Thunder Wave > Toxic
~ Stealth Rock > Flamethrower
---------
Wish support from Blissey is so reliable, and with protect it can also heal itself and scout for choice moves. Protect seems especially useful when so many trick Gengars are around. Thunder Wave is to scare off some opponents that might otherwise come in to set up on Blissey. Stealth Rock support is always welcoming, especially with soooooo many Skymin around… -_-“
Edit: Toxic + Wish + Protect to stall Swampert, among other things. Flamethrower as a backup strategy for Luke/Hera switch ins. Since Blissey no longer has SR it won't lead anymore. Probably lead with Gyarados.
Zapdos @ Leftovers
Modest / Pressure
252 HP / 220 Def > 220 SpD / 38 Spe
~ Thunder Bolt
~ Hidden Power Ice
~ Roost
~ Roar > Sleep Talk
--------
My physical tank, phaser, and counter for Skymin, Gyarados, and possibly Salamence. Of course it can scare of many other things too and Roost off the damage.
Edit: I'm not sure if this will work but Sleep Talk can absorb Sleep, which then blocks other status, and I got Blissey to share the role of status sponge. SubRoost Zapdos beating my team is a good point, but if has Heatwave to beat my Magnezone and Scisor then it shouldn't have Hidden Power Ice so hopefully my Zapdos would win in the end.
Gyarados @ Leftovers
Adamant / Intimidate
216 HP / 16 Atk / 176 Def / 100 Spe
~ Dragon Dance
~ Taunt
~ Water Fall
~ Earthquake > Ice Fang
--------
The standard bulky Gyarados set. Mainly utilize intimidate to cause switches, and depending on what I predict they will switch into, I might switch out Triple-Moles or Magnezone to trap! Gyarados also serves to bait electric attacks which the Moles are immune to, so that it’s safer to switch the fragile Moles in. P.S. Should I change it to Suicine with Hidden Power Grass + Surf + CM + Rest.
Edit: Ice Fang for Salamence. Hmm, I agree its SR weak make it not suitable for multiple switch-ins, but now that Zapdos can no longer share the role of physical walling I think I need to keep it bulky. Hopefully Blissey's Wish support can keep it alive longer.
Scizor @ Life Orb
Adamant / Technician
252 HP / 252 Atk / 6 Spe
~ Sword Dance
~ Bullet Punch
~ X-Scizor
~ U-Turn > Baton Pass
--------
Everone has a similar Scizor now so the first 3 moves should be obvious. Ideally I will U-Turn immediately when it’s still early/mid game, hoping that something like Infernape/Heatran will switch in. If they do, then I switch into my Scarf Mole-Brothers to finish them off. As mentioned, late game it will come out to attempt a sweep!
Edit: I got a Baton Pass with 0 Spe EV investment because I think Scizor is too slow to outspeed any major threat anyway. So the strategy is similar to when I used U-Turn. Early to mid game I switch into something that will switch out, opponents expect me to SD so they switch in something that will force me out but in fact I use Baton Pass without doing the SD. If they switch in their Inferape, Heatran, or even Skarmory to Whirlwind me, Moles and Magnezone will take care of them.
Dugtrio @ Choice Scarf
Adamant / Arena Trap
130 HP / 252 Atk / 128 Spe
~ Earthquake
~ Sucker Punch
~ Aerial Ace
~ Stone Edge
--------
STAB Earthquake will be used most of the time to kill fire and electric types that threaten Gyarados and Scizor. I chose scarf because I also want to faint Jolteon, scarf Heatran, and scarf Haracross. Stone Edge isn’t too useful besides trap-fainting Weavile (flying types can switch) so I was thinking should I change to Naughty nature and use Hidden Power Grass for Swampert? How much damage would I do?
Edit: Kept Sucker Punch to hit other priority move users.
Magnezone @ Leftovers
Modest / Magnet Pull
172 HP / 252 SpA / 86 Spe > 66 HP / 252 SpA / 192 Spe
~ Thunder Bolt
~ Hidden Power Fire > Hidden Power Grass
~ Substitute
~ Magnet Rise
--------
Magnet Rise and Substitute to take away it’s 4x ground weakness and prevent status or explosion from Bronzong/Forretress. Thunder Bolt is a powerful STAB and is a staple move. Hidden Power Fire is for Scizor/Forrey/Bronzong/Metagross etc. and I assumed the typical EV spread for Scizor now is 0 in Spe because of the priority move Bullet Punch, so hopefully I can burn it before it U-Turns away.
Edit: Changed to Hidden Power Grass to take care of Swampert that loves to switches in, or to revenge kill CursePert with Rest who won't be afraid of Blissey's toxic stall. Also made it faster to trap Metagross >.<"
Edit: Bolded words are changes that I've made according to everyone's helful suggestions. I've learnt so much, not just for this team, but in terms of what needs to be considered when team building. Thank you all!
Note: Latest changes are made after considering suggestions up to Bogmire's post.

Blissey @ Leftovers
Calm / Natural Cure
6 HP / 252 Def / 252 SpD
~ Wish
~ Protect
~ Thunder Wave > Toxic
~ Stealth Rock > Flamethrower
---------
Wish support from Blissey is so reliable, and with protect it can also heal itself and scout for choice moves. Protect seems especially useful when so many trick Gengars are around. Thunder Wave is to scare off some opponents that might otherwise come in to set up on Blissey. Stealth Rock support is always welcoming, especially with soooooo many Skymin around… -_-“
Edit: Toxic + Wish + Protect to stall Swampert, among other things. Flamethrower as a backup strategy for Luke/Hera switch ins. Since Blissey no longer has SR it won't lead anymore. Probably lead with Gyarados.

Zapdos @ Leftovers
Modest / Pressure
252 HP / 220 Def > 220 SpD / 38 Spe
~ Thunder Bolt
~ Hidden Power Ice
~ Roost
~ Roar > Sleep Talk
--------
My physical tank, phaser, and counter for Skymin, Gyarados, and possibly Salamence. Of course it can scare of many other things too and Roost off the damage.
Edit: I'm not sure if this will work but Sleep Talk can absorb Sleep, which then blocks other status, and I got Blissey to share the role of status sponge. SubRoost Zapdos beating my team is a good point, but if has Heatwave to beat my Magnezone and Scisor then it shouldn't have Hidden Power Ice so hopefully my Zapdos would win in the end.

Gyarados @ Leftovers
Adamant / Intimidate
216 HP / 16 Atk / 176 Def / 100 Spe
~ Dragon Dance
~ Taunt
~ Water Fall
~ Earthquake > Ice Fang
--------
The standard bulky Gyarados set. Mainly utilize intimidate to cause switches, and depending on what I predict they will switch into, I might switch out Triple-Moles or Magnezone to trap! Gyarados also serves to bait electric attacks which the Moles are immune to, so that it’s safer to switch the fragile Moles in. P.S. Should I change it to Suicine with Hidden Power Grass + Surf + CM + Rest.
Edit: Ice Fang for Salamence. Hmm, I agree its SR weak make it not suitable for multiple switch-ins, but now that Zapdos can no longer share the role of physical walling I think I need to keep it bulky. Hopefully Blissey's Wish support can keep it alive longer.

Scizor @ Life Orb
Adamant / Technician
252 HP / 252 Atk / 6 Spe
~ Sword Dance
~ Bullet Punch
~ X-Scizor
~ U-Turn > Baton Pass
--------
Everone has a similar Scizor now so the first 3 moves should be obvious. Ideally I will U-Turn immediately when it’s still early/mid game, hoping that something like Infernape/Heatran will switch in. If they do, then I switch into my Scarf Mole-Brothers to finish them off. As mentioned, late game it will come out to attempt a sweep!
Edit: I got a Baton Pass with 0 Spe EV investment because I think Scizor is too slow to outspeed any major threat anyway. So the strategy is similar to when I used U-Turn. Early to mid game I switch into something that will switch out, opponents expect me to SD so they switch in something that will force me out but in fact I use Baton Pass without doing the SD. If they switch in their Inferape, Heatran, or even Skarmory to Whirlwind me, Moles and Magnezone will take care of them.

Dugtrio @ Choice Scarf
Adamant / Arena Trap
130 HP / 252 Atk / 128 Spe
~ Earthquake
~ Sucker Punch
~ Aerial Ace
~ Stone Edge
--------
STAB Earthquake will be used most of the time to kill fire and electric types that threaten Gyarados and Scizor. I chose scarf because I also want to faint Jolteon, scarf Heatran, and scarf Haracross. Stone Edge isn’t too useful besides trap-fainting Weavile (flying types can switch) so I was thinking should I change to Naughty nature and use Hidden Power Grass for Swampert? How much damage would I do?
Edit: Kept Sucker Punch to hit other priority move users.

Magnezone @ Leftovers
Modest / Magnet Pull
172 HP / 252 SpA / 86 Spe > 66 HP / 252 SpA / 192 Spe
~ Thunder Bolt
~ Hidden Power Fire > Hidden Power Grass
~ Substitute
~ Magnet Rise
--------
Magnet Rise and Substitute to take away it’s 4x ground weakness and prevent status or explosion from Bronzong/Forretress. Thunder Bolt is a powerful STAB and is a staple move. Hidden Power Fire is for Scizor/Forrey/Bronzong/Metagross etc. and I assumed the typical EV spread for Scizor now is 0 in Spe because of the priority move Bullet Punch, so hopefully I can burn it before it U-Turns away.
Edit: Changed to Hidden Power Grass to take care of Swampert that loves to switches in, or to revenge kill CursePert with Rest who won't be afraid of Blissey's toxic stall. Also made it faster to trap Metagross >.<"