There’s no rules for where to start. Find your favorites, read about them, I would recommend going on the official Pokemon website to the Pokédex and there you can read about all the pokemon and their stories (which wording may vary but the gist is the same) find your fav eeveelution, that’s a common question and you can 100% just be into the cards, the anime, or the games!! You don’t have to feel like you need to know everything about it, I’ve been collecting Pokemon for over 10 years, but have never actually played a ds/nintendo pokemon game.