Birthday party ideas?

I have been stressing for a while now about what I wanna do fo my 13th birthday. I think I have decided that I do not have to go anywhere to have a good time for my birthday. I am thinking about basically just a "Backyard BBQ". Invite about 20 people (Boys and girls), Turn the stereo on high and eat hamburgers, hotdogs, ect. But I need some more ideas. I do not want to do as it entertaining wise, such as games and stuff. Maybe stuff to rent or something. Also More and different stuff to eat. Any other suggestions are needed. Oh, and it HAS TO BE CHEAP!!!!! Thank you so much!