I like the fact that your garchomp has high attack. If he has high special attack, mabe have flamethrower to go against ice because it is more powerful than stone edge or brick break, but those arn't bad either. If garchomp has alot of happines & you want a sweeper which garchomp wouldn't be bad at, then teach him dragon rush or outrage instead of dragon claw. Earthquake is really good with offensive pokemon (unlike shuckle) so it is a very good addition plus it gets STAB. If you feel you need a power up, try workup( if Sp attack is used or swords dance if only attack. It depends on your stategy, style of battling, preferences, & whom you are battling.
Good item- dragon fang if sweeping with dragon type move)/(if alot of hp only) life orb
EVs 252 attack, 252speed, 4 hp or Sp attack
Ability- rough skin or if used in desert or something sand veil
Good partner- someone with sand stream or with fire & or dragon moves.
Nature- adamant (if not using flame thrower) naughty (if using flamethrower)