I am stuck at which theme I should do?

Well, I haven't had a good birthday in a very long time and I will be getting a job this summer so I want to have a party that I can enjoy. I kind of want to do a movie theme, but I am stuck on what to do. I also love Broadway. I don't know though. I am stuck on both. I want it to be kind of extravagant but we're not very rich and we don't have much money to work with. Can anyone help me out?