Trying to make a team, stopped after Ruby/Sapphire so I'm completely new to this and honestly only picked pokemon I like.

Volcarona - Flame Body SpeA/Spe
Fiery Dance
Bug Buzz
String Shot
Quiver Dance

Greninja - Protean SpeA/Spe
Ice Beam
Hydro pump
Extrasensory
Dark Pulse
Thinking of throwing U-turn in there, but since he's so fast... not sure.

Gardevoir - synchronize SpeA-Spe
Moonblast
Thunderbolt
Psychic
Calm Mind

Mega Mawile - intimidate Attack/HP
Iron Head
Sucker Punch
Play Rough
Fire Fang

I'm not really sure where to go from here, as I don't know a whole lot about team building, going for coverage I know I'm completely lacking as far as grass, dragon, fighting, ghost, poison, ground and rock go.

I was thinking Lilligant or Breloom for grass[/fighting] but I'm having issues breeding Lilligant and I don't know if Breloom is even viable. Garchomp covers some of this I know, but I also know he's pretty much a cookie cutter pokemon and he's not one of my favorites anyway.

Was also thinking
Gourgeist SpeD/Spe
Substitute
Trick-r-Treat
Phantom Force
Leech Seed

Any suggestions are helpful, thank you.