[RATE MY TEAM] Help improving my team.

[Flaine]

Hello, this is my first post.Really happy to become part of this community!

I would like to have some advice about my current team. I have been trying to build a team for competitive play but before actually building it in ORAS (soon in Sun), I have been using it in Showdown. 

I have had some victories but at the same time I have had a ton of lost matches in which i couldn't do too much.

Therefore, I would love to get some help into improving or even building a new team.

I started with this:

Arcanine @ Weakness Policy  
Ability: Intimidate  
EVs: 252 HP / 56 Def / 200 SpD  
Careful Nature  
- Morning Sun  
- Will-O-Wisp  
- Flare Blitz  
- Wild Charge  

Chesnaught @ Assault Vest  
Ability: Bulletproof  
EVs: 252 HP / 252 Atk / 4 Def  
Adamant Nature  
- Seed Bomb  
- Power-Up Punch  
- Drain Punch  
- Rock Tomb  

Scizor @ Life Orb  
Ability: Technician  
EVs: 252 HP / 252 Atk / 4 SpD  
Adamant Nature  
- Roost  
- X-Scissor  
- Bullet Punch  
- Swords Dance  

Rotom-Wash @ Leftovers  
Ability: Levitate  
Shiny: Yes  
EVs: 250 HP / 252 SpD / 8 Spe  
Calm Nature  
- Hydro Pump  
- Confuse Ray  
- Will-O-Wisp  
- Charge Beam  

Snorlax @ Chesto Berry  
Ability: Immunity  
EVs: 156 HP / 252 Def / 100 SpD  
Impish Nature  
- Stockpile  
- Rest  
- Crunch  
- Belly Drum  

Charizard-Mega-Y (M) @ Charizardite Y  
Ability: Drought  
EVs: 4 HP / 252 SpA / 252 Spe  
Modest Nature  
- Flamethrower  
- Focus Blast  
- Solar Beam  
- Air Slash  

Then i switched  charizar with:

Latios-Mega @ Latiosite  
Ability: Levitate  
EVs: 252 HP / 252 Spe  
Timid Nature  
IVs: 0 Atk  
- Calm Mind  
- Roost  
- Psyshock  
- Dragon Pulse

And now my team actually looks like this:

Dragonite @ Choice Band  
Ability: Multiscale  
EVs: 4 HP / 252 Atk / 252 Spe  
Jolly Nature  
- Fire Punch  
- Outrage  
- Extreme Speed  
- Thunder Punch  

Arcanine @ Weakness Policy  
Ability: Intimidate  
EVs: 252 HP / 56 Def / 200 SpD  
Careful Nature  
- Morning Sun  
- Will-O-Wisp  
- Flare Blitz  
- Wild Charge  

Gardevoir @ Sitrus Berry  
Ability: Synchronize  
EVs: 252 HP / 252 Def / 4 SpD  
Calm Nature  
- Will-O-Wisp  
- Calm Mind  
- Confuse Ray  
- Draining Kiss  

Scizor @ Scizorite  
Ability: Technician  
Happiness: 0  
EVs: 252 HP / 252 Atk / 4 SpD  
Adamant Nature  
- Bullet Punch  
- Swords Dance  
- Roost  
- X-Scissor  

Rotom-Wash @ Leftovers  
Ability: Levitate  
Shiny: Yes  
EVs: 250 HP / 252 SpD / 8 Spe  
Calm Nature  
- Hydro Pump  
- Confuse Ray  
- Will-O-Wisp  
- Charge Beam  

Snorlax @ Chesto Berry  
Ability: Immunity  
EVs: 156 HP / 252 Def / 100 SpD  
Impish Nature  
- Stockpile  
- Rest  
- Crunch  
- Belly Drum  

What do you think i should do to improve?

Finally, I always want to build my teams around a fire-type Pokemon because that is my favorite type,but I think I haven't been able to balance my team in a way in which my pokemon could actually shine.

Thank You!