Jolly might be the best, because then Salamence, Pikachu, and Celebi will not be faster than your Garchomp, and you can outrun faster Pokémon such as Gengar.
Fire Fang Crunch Dragon Dance Substitute Protect
Another good idea if you want to do this is to give it a Yache Berry to hold. This will let your Garchomp survive most Ice type attacks.
