Help me build a VGC '15 team?

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I've been following VGC for the past year or so, but only got really involved in battling this past summer... and I'm not too great at building teams.
EDIT: Here's a team I've been using on Smogon that I've been doing decent with. Thoughts/Advice?


Cresselia @ Leftovers
Ability: Levitate
Level: 50
Shiny: Yes
EVs: 252 HP / 252 SpA / 4 SpD
Modest Nature
- Icy Wind
- Protect
- Moonblast
- Psychic


Flying Thing (Landorus-Therian) @ Choice Scarf
Ability: Intimidate
EVs: 248 HP / 164 Def / 96 Spe
Jolly Nature
- Knock Off
- Rock Slide
- Earthquake
- U-Turn


Dragon Tales (Salamence) (F) @ Salamencite
Ability: Intimidate
Level: 50
EVs: 252 Atk / 6 Def / 252 Spe
Jolly Nature
- Hyper Voice
- Draco Meteor
- Roost
- Fire Blast


Washy Wash (Rotom-Wash) @ Sitrus Berry
Ability: Levitate
Level: 50
EVs: 252 HP / 4 SpA / 252 SpD
Calm Nature
- Hydro Pump
- Protect
- Thunderbolt
- Will-O-Wisp


Bisharp (M) @ Life Orb
Ability: Defiant
Level: 50
Shiny: Yes
EVs: 252 Atk / 4 SpD / 252 Spe
Adamant Nature
- Knock Off
- Sucker Punch
- Iron Head
- Protect


i'm sorry (Smeargle) (M) @ Focus Sash
Ability: Technician
Level: 50
Shiny: Yes
EVs: 84 HP / 128 Def / 44 SpD / 252 Spe
Jolly Nature
- Dark Void
- Follow Me
- Fake Out
- Ice Beam