The best Pokemon TCG Pocket ex Starter deck is probably the Dark-type Paldean Clodsire ex deck, at least at time of writing, but in reality the answer is a lot more complicated than that. There are nine ex Starter decks in PTCGP that players can pick between once they complete the associated challenge missions,

If you want a deck to use as a basis upon which to build an even better deck, the Water-type Wugtrio ex starter deck is the best way to go. Not only is Wugtrio ex a pretty fantastic Pokémon ex card in its own right, but the deck also includes the fantastic combo of Tatsugiri and Dondozo — two strong basic cards that complement each other very well.

Going first in Pokémon TCG Pocket sucks. You can’t equip any energy (unless you happen to have Misty). You can’t evolve. You kind of just put a Pokémon in the active spot and hope that your opponent doesn’t wallop you too hard on the second turn. It’s pretty rough — that is, until Giratina ex showed up to alleviate your woes.