Unfortunately, Garchomp cannot use Special Energy like Double Rainbow or Scramble Energy (these turn off its PokeBody), so it takes quite awhile to get off of the ground
There are a few cards that are expensive and are cEDH staples, but they are just very good cards and should not see much of a bump
Carmen does cost five, though, so the rest of your deck should be filled with equal amounts of recursion (Sevinnes Reclamation et al), ramp (Ancient Tomb, Sword of the Animist) and evasive bodies that can also grow tall (Voldaren Bloodcaster, Liberator, Urzas Battlethopter, Serra Ascendant)
Once per turn, by resting one card while a character with a cost of 5 or more occupies the field, players can set up to three rested DON
Other cards that interact with putting counters on it will interact with this effect accordingly