You should do some research on copyright infringement first. You can be sued for using trademarked things, like "pokemon". It doesn't matter if you don't make money, or release it for free, the fact that it exists at all can be seen as damaging the official name, and you can be sued over it. Feel free to look into it, it happens all the time to tetris clones.
That said, there's nothing wrong with having a collectable creature game, that's heavily inspired by pokemon. Just don't use the actual word "pokemon" or any of the pokemon from any of the games/shows in your game.