Hi Smogon. New here and all that stuff. I come here to get some advice from the wisest people. This March is my second VGC and I don't want to screw it like last time where I picked some random mons to get through.
If I forgot anything or I broke any random rule just let me know.
This is the team so far:
Hitmontop (F) @Sitrus Berry
Ability: Intimidate
EVs: 248HP / 252Atk / 8 Spe
Adamant Nature (+Atk -SpA)
Fake Out
Close Combat
Sucker Punch
Detect
My fake Out user. Intimidate slighly cripples the other guy, while Close Combat provides some raw power. The Sitrus berry is good for some extra HP to keep fighting or to switch it, letting me use another Fake Out later. A well timed Sucker Punch gets rid of ghost, psychics or more speedy foes. The EVs are there to outspeed another Htops.
Metagross @Rock Gem
Ability: Clear Body
EVs: 252HP / 252Atk / 4SpD
Adamant Nature (+Atk -SpA)
Bullet Punch
Rock Slide
Earthquake
Protect
The bulky attacker. It can take any hit, dealing even with fire. Rock Slide + Rock Gem is something people usually don't expect. Earthquake is there for some ground coverage, and bullet punch to finish the poor guy's life.
Tyranitar (F) @Focus Sash
Ability: Sand Stream
EVs 252HP / 252Atk / 4SpD
Adamant Nature (+Atk - SpA)
Rock Slide
Crunch
Low Kick
Protect
A pretty average Ttar. Sand stream slowly kills the other one and works well with Garchomp's Sand Veil. Crunch is there to take down ghosts or psychics as Latios. Focus Sash prevents him for being killed by fight Pokémon in order to counter them back.
Garchomp (F) @Dragon Gem
Ability: Sand Veil
EVs 252HP / 252Atk / 4SpD
Adamant Nature (+Atk - SpA)
Dragon Claw
Earthquake
Rock Slide
Protect
Sometimes it struggles against Latios/Latias. The rest of the time it just kills everything. Before I had Dual Chop for Substitutes, but the lack of accuracy was a bigger risk.
Thundurus (M) @Charti Berry
Ability: Prankster
EVs 252HP / 252SpA / 4Def
Modest Nature (+SpA -Atk)
Thunderbolt
Hidden Power Flying
Thunder Wave
Protect
Prankster + Thunder Wave for some free paralysis. Hidden Power Flying for flying coverage and Thunderbolt for stab.
Cresselia (F) @Leftovers
Ability: Levitate
EVs 252HP / 128Def / 128SpD
Calm Nature (+SpD -Atk)
Ice Beam
Energy Ball
Toxic
Protect
Ice and Energy Ball are there to add more coverage. Toxic + the deffensive EV Spread for stalling. Levitate has good psynergy with earthquake.
Comments:
Generally I will use the first four, who are pretty damn good together, adding Thundurus when I see some water type in team preview.
I know I have too many Rock Slides, but they saved me lots of times.
Not really sure about the last two, specially Cresselia, any suggestion will be welcome. I wonder what else could I get to cover up the hole I have against Fight/Water/Grass/Ground types.
Also, there is not so much speed due to face an incoming Trick Room, while getting the extra HP. Wondering if I should use a -Spe nature on the slower mons such as Tyranitar or Metagross and even Htop for this purpose.
Feel free to rate, suggest, and comment. EVs spreads, moves, another Pokémon or whatever you may find usefull :)
If I forgot anything or I broke any random rule just let me know.
This is the team so far:

Hitmontop (F) @Sitrus Berry
Ability: Intimidate
EVs: 248HP / 252Atk / 8 Spe
Adamant Nature (+Atk -SpA)
Fake Out
Close Combat
Sucker Punch
Detect
My fake Out user. Intimidate slighly cripples the other guy, while Close Combat provides some raw power. The Sitrus berry is good for some extra HP to keep fighting or to switch it, letting me use another Fake Out later. A well timed Sucker Punch gets rid of ghost, psychics or more speedy foes. The EVs are there to outspeed another Htops.

Metagross @Rock Gem
Ability: Clear Body
EVs: 252HP / 252Atk / 4SpD
Adamant Nature (+Atk -SpA)
Bullet Punch
Rock Slide
Earthquake
Protect
The bulky attacker. It can take any hit, dealing even with fire. Rock Slide + Rock Gem is something people usually don't expect. Earthquake is there for some ground coverage, and bullet punch to finish the poor guy's life.

Tyranitar (F) @Focus Sash
Ability: Sand Stream
EVs 252HP / 252Atk / 4SpD
Adamant Nature (+Atk - SpA)
Rock Slide
Crunch
Low Kick
Protect
A pretty average Ttar. Sand stream slowly kills the other one and works well with Garchomp's Sand Veil. Crunch is there to take down ghosts or psychics as Latios. Focus Sash prevents him for being killed by fight Pokémon in order to counter them back.

Garchomp (F) @Dragon Gem
Ability: Sand Veil
EVs 252HP / 252Atk / 4SpD
Adamant Nature (+Atk - SpA)
Dragon Claw
Earthquake
Rock Slide
Protect
Sometimes it struggles against Latios/Latias. The rest of the time it just kills everything. Before I had Dual Chop for Substitutes, but the lack of accuracy was a bigger risk.

Thundurus (M) @Charti Berry
Ability: Prankster
EVs 252HP / 252SpA / 4Def
Modest Nature (+SpA -Atk)
Thunderbolt
Hidden Power Flying
Thunder Wave
Protect
Prankster + Thunder Wave for some free paralysis. Hidden Power Flying for flying coverage and Thunderbolt for stab.

Cresselia (F) @Leftovers
Ability: Levitate
EVs 252HP / 128Def / 128SpD
Calm Nature (+SpD -Atk)
Ice Beam
Energy Ball
Toxic
Protect
Ice and Energy Ball are there to add more coverage. Toxic + the deffensive EV Spread for stalling. Levitate has good psynergy with earthquake.
Comments:
Generally I will use the first four, who are pretty damn good together, adding Thundurus when I see some water type in team preview.
I know I have too many Rock Slides, but they saved me lots of times.
Not really sure about the last two, specially Cresselia, any suggestion will be welcome. I wonder what else could I get to cover up the hole I have against Fight/Water/Grass/Ground types.
Also, there is not so much speed due to face an incoming Trick Room, while getting the extra HP. Wondering if I should use a -Spe nature on the slower mons such as Tyranitar or Metagross and even Htop for this purpose.
Feel free to rate, suggest, and comment. EVs spreads, moves, another Pokémon or whatever you may find usefull :)