Replying to Going to Senior Prom as a Sophmore

I know exactly nothing about prom. I was asked by this ski chick i chill with who is wicked rich and needs a date to her senior prom (she's a solid 8.5). Being a young poor ski bum who's parents are ass holes I will have to try to be ballin on a budget. It will be with a high end boarding school so whats up with like prespster/douche style now a days? Rent or buy a tux? Does Saga make tuxes? Jiberish?? Also how do I get my parents to let me after party? Generally prom tips would be nice. I know that there'salready like probably at least 20 threads on this but whatever.