The Wartortle is more of a "just in case" card, since most people will just skip that stage with Rare Candy, which allows you to put a Stage 2 (Blastoise) straight onto the Basic (Squirtle). Other 1-ofs are usually simply a "this card will be helpful iI I get it, but it won't be the end of the world if I don't", similar to Magic. The difference is with the speed you go through your deck compared to Magic, through drawing and searching, you probably will eventually find it. Unless its prized.
Besides that, as a player of Magic and Pokemon (although I hop between them a lot), welcome! Just drop off your sense of card advantage at the door, it basically doesn't exist here, you'll be discarding 3 cards to get 1 and it'll be worth it, and turning 1 card into many more all the time. And be warned, the gap between meta decks and casual decks is MUCH bigger here than in Magic, at least from what I've seen. Besides that, its a fun game, and a good change of pace from Magic. Plus, the competitive scene is much easier to get into.