Uh, Uchiha, you do realize that Boundary has no effect whatsoever on anything not weak to colorless, which is Garchomp's actual type, right? Since, y'know, Garchomp's body does NOT alter his type. You're thinking of Porygon-Z.
Anyway, there are a few options.
- Smeargle SW for the start. Can be backed up by Pachirishu, so you play like 4 Pachi 2 Smeargle 434 Garchomp.
- Aerodactyl with Holon Fossil. Not smart to play Mysterious Fossil in a deck with so few other basics.
- MagneCatty engine. Gets you the energy when you need it. Leaves little room for a good starter though, and a huge Battle Frontier weakness.
Thats what I'd pick from.