Perhaps one of the pokemon trainers would work? They're 10 so of course their outfits aren't that skimpy or crazy, a great place to start. Or you could be a hogwarts student, which would actually mean sewing things as opposed to just buying a bunch of things at a clothing store like you could probably do for most of the (simpler) trainers. Also, have you considered gjinkas? If you're up to it you could probably design something based on, say, your favorite pokemon?