The first few are easy at least.
1-3 are grass starter, 4-6 are fire starter, 7-9 are water starter. Then you know bugs are next, which take up 6 slots. You should remember regional bird line is directly after that. And right next to the bird is the rat.
That's already the first 20 in kanto without looking anything up. If I remembered Fearow was right after Rattata, and Ekans is there for some reason, then I would've gotten up to 26 because Pikachu being 25 and Meowth being 52 is pretty standard trivia.
