I'd sign up for Pokenations since summer is coming and i need to improve my skills, but how good are the battlers here? I don't want to be an useless teammate since a good majority of the people i know are quite good at battling
Seriously, don't think about whether you're going to be useless or not. I would say just sign up. I think it's going to be a really fun experience for you
Everyone is welcome and no one is unwelcome. Don't think yourself useless; there'll naturally be a few people who have more experience, but you can trust the creators to ensure that all people are evenly placed so as to provide that everyone is comfortable and no one feels out of place.