I don't know what to do for my thirteenth birthday party?

hi, im turning 13 in august. money's a little tight right now so i can't have a big bash for my 13th. im probably going to have the party at my house and we have a pool. i don't want a theme but i do have colors: black and white. can you give me some ideas on how to throw an inexpensive party with lots of kids? thanks.