"GARCHOMP is good when there are alot of variety of energy cards"
most decks that garchomp can fit into are dual type decks or the deck like the pre-constructed EX-TRR
since the cards from that deck uses three energy types...
so just choose a set of pokemon types well... make a a thing called "side board" in MTG... i mean a set of cards that you can use to swap cards from your previous deck to make garchomp useful...
Orrr you could just obtain 2 energies of every type except Metal, and you're set as well? Buying theme decks gives you >10 of the same energy, that's not what I'd want if I would play Garchomp.
Why not Metal? 8 energy types (other then (C) ) total is 16 energy. Smeargle DP3 is really needed though -_- Just play it with pokemon that only use colorless attacks.