I beleive that GG works by doing lots of damage with Gallade and killing your Poke-Powers with Gardy. Oh, and Gardy's power lets it use supporters in your discard pile, so beware if you use Team Galactic's Wager. Also, Gardevoir X will destroy Eeveelutions, so if you are using them, find some way to kill it quick, as it can switch with its power.