One idea is to go the "fiesta" route. Mexican foods are great to prepare ahead of time and are easy on the budget as well. With a Layered Dip and chips, some enchiladas and a good Spanish rice, you're all set. Margaritas anyone?
A taco bar is an easy addition to the foods above or stands alone perfectly fine. Ole~!

A sweet friend of mine reminded me recently of the Baked Potato Bar--which was seriously popular in the 80's party-world. What a good idea it was...and still is. Who doesn't enjoy a plump, steaming spud piled high with all the good stuff??
Delicious, economical, and filling, what's not to love?