Prom Attire

I am 17 years old, and will be attending my first formal dance (Prom). The theme is a masquerade party. What do I need to dress appropriately? I am not in a situation to spend a whole lot of money on a tuxedo, so I was wondering what I could piece together a nice outfit. I already have black dress shoes and black slacks. What else do I need? On a side note, i am 5"10 and stalky if that matters, and my dates' dress is all black, so should I get all black attire as well?