Like others said if your thinking of a DJ that will be costly right there. If it is going to be going on during dinner time you really do have to serve something so I'm thinking pizza would be the cheapest? Add chips and soda. Birthday cake...
My DD is turning Sweet 16 in October

I've rented two rooms at a brand new luxury resort and she is only having her 4 closest friends to spend the night. They will swim and all go to the spa. I'm having a limo bring the girls up to the resort where I will meet them as I want to go up ahead and set up the rooms.
I got the cutest gifts online for the girls that are coming...Sweet 16 candy bars personalized, sweet 16 candles, sweet 16 key chains, I got pink lei's and neon pink glowing sunglasses for them to wear at the resort. Then they have neon margarhita glasses that I'm filling with punch and they glow different colors

She also has a Sweet 16 pillow in the shape of a purse that the girls can all sign during the sleepover. Plus a few small tins that I have personalized Sweet 16 stickers on that I will fill with candy.
I'll decorate the room with Sweet 16 decorations plus I'm having a cute 2 tiered cake made. My friend is doing it free plus making goodie bags for all the girls with things like caramel/chocolate apples, dipped pretzel rods, etc
That's all I'm doing because DH and I are buying her a car instead of a big party