For the boning, the cheapest option is to buy zip ties. They give way better support than the cheap, flimsy plastic kind, and are a lot easier to work with than metal.
Mami's the most mature looking one, so you could probably do slightly heavier makeup than you would for the other girls. I think sticking with a natural colour scheme is probably best though, they ARE still highschool girls after all. I'm sure you'll figure out something nice