ORAS OU First Team; How can I improve it?

[Mikaphewn]

Proto Man (Scizor) @ Choice Band
Ability: Technician
EVs: 248 HP / 252 Atk / 8 Spe
- Bullet Punch
- U-turn
- Superpower
- Pursuit

Scisor used as the lead. He has a priority move for weak Pokemon, Superpower for normal types, pursuit for predicted switches, and U-turn to retreat



(Azumarill) (F) @ Choice Band
Ability: Huge Power
EVs: 248 HP / 252 Atk / 8 SpD
Adamant Nature
- Aqua Jet
- Waterfall
- Play Rough
- Belly Drum

Here is where I'm not sure. Belly drums require good timing and prediction which I simply don't have. I wanted Belly Drum and Aqua jet and the Choice Band to synergize with each other


(Chansey) @ Eviolite
Ability: Natural Cure
EVs: 4 HP / 252 Def / 252 SpD
Bold Nature
- Toxic
- Soft-Boiled
- Protect
- Wish

My "Healer". Protect to stall with toxic or Wish. Wish to heal herself or Azumarill (or any other weak Poke)


Gengar (M) @ Life Orb
Ability: Levitate
EVs: 252 SpA / 4 SpD / 252 Spe
Timid Nature
- Shadow Ball
- Sludge Wave
- Focus Blast
- Taunt

The "sweeper" of the team. Shadow Ball and Sludge wave for the STAB. Taunt for people attempting to set up, but I'm not sure what Focus blast is for

(Gardevoir-Mega) (F) @ Gardevoirite
Ability: Trace
EVs: 16 HP / 8 Atk / 232 SpA / 252 Spe
Timid Nature
- Hyper Voice
- Psyshock
- Focus Blast
- Will-O-Wisp

Outspeed and one shot is M-Gardevoir's goal. She has Psyshock for the STAB, but I don't know what to make the other moves

(Rotom-Wash) @ Leftovers
Ability: Levitate
EVs: 248 HP / 252 Def / 8 Spe
Bold Nature
- Volt Switch
- Hydro Pump
- Will-O-Wisp
- Pain Split

My "Filler" Pokemon. I don't really have a set "role" for him yet. I mainly just use him where M-Gardevoir and Azu isn't the best choice to use. I am very open to changing him for another Pokemon

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This is my first team. I don't know how to build a team or what makes a Pokemon good for a team. Can someone include some tips or a guide for basic team building?

I'm open to criticism, but please keep in mind I have almost no experience with competitive.

 

[rice pudding]

You could change the Rotom-Wash to Volcanion because it beats a few things that beat Azumarill/Gengar/Mega Gardevoir such as Scizor. Also you should change your Azumarill set to the one I put in the spoiler, which will allow you to outspeed Rotom-W and kill it with Play Rough if you manage to get a Belly Drum off safely. I don't like Chansey's place on this team and you need Stealth Rocks to benefit your Sweepers so I would change that for a Defensive Lando-T which also beats Pokémon like Excadrill and Talonflame that kinda run through you, it will also help you gain momentum with U-Turn (as does Scizor). I know this will stop you from passing Wish's but in my opinion it would be a better option. You should also change the Attack IV's on Gengar and Gardevoir to 0 so that Foul Play will do less.

Hide

Azumarill @ Sitrus Berry
Ability: Huge Power
EVs: 252 Atk / 252 Spe
Jolly Nature
- Belly Drum
- Aqua Jet
- Play Rough
- Knock Off

Volcanion @ Choice Specs
Ability: Water Absorb
EVs: 252 HP / 252 SpA
Modest Nature
IVs: 0 Atk / 30 SpA
- Steam Eruption
- Fire Blast
- Sludge Bomb / Sludge Wave
- Hidden Power [Grass]

Landorus-Therian @ Rocky Helmet
Ability: Intimidate
EVs: 252 / 240 Def / 8 SpD / 8 Spe
Impish Nature
- Earthquake
- U-turn
- Stone Edge
- Stealth Rock

Hope I helped and sorry if my rate isn't the best, I'm pretty new to rating.

 

[thekeytoyourheart]

This link will help you to know the basics of the various metagames: http://www.smogon.com/forums/threads/useful-resources-for-learning-new-metagames.3558515/. From then on you can learn about the roles of each Pokemon in the metagame, good team cores, and sample teams.
Here's a useful guide to team building: http://www.smogon.com/forums/threads/teambuilding-guide.3552468/

For your Azumarill, go for a Choice Band set or a Belly Drum set, as Choice Band locks Azumarill into one attacking move. For Choice Band Azumarill, the last move could be Superpower or Knock Off (coverage vs. utility). If you want to pull of a Belly Drum sweep, use the set recommended by rice pudding.

Gengar's Focus Blast is for steel, dark, ice, and rock types such as Tyranitar, Weavile, Bisharp, Ferrothorn, Excadrill, and Heatran that would take little damage from Gengar's STAB moves.

As Mega Gardevoir is a special wallbreaker, you can shift 8 Atk EVs to Defense. Focus Blast does hefty damage to steel types that would otherwise wall Mega Gardevoir. However, Bullet Punch from Scizor, Mega Scizor, and Mega Metagross will OHKO Mega Gardevoir. Will-O-Wisp can burn steel types on the switch-in and slower steel types. Rotom-Wash is a defensive pivot that has good synergy with Mega Gardevoir. Rotom-W can take steel type attacks for Mega Gardevoir and can burn Mega Gardevoir's counters with Will-O-Wisp.