The post before mine answers this total thread. And please do not use random smilies. That's one of the rules. I would stick to raising those first ones you capture for a bit, because it's going to get harder ahead when you play.
Most of it is already explained by previous posters, but you HAVE to Snag Teddiursa. You might want to level him up as Ursaring does huge damage if you treat him nicely and use Return.