Chicken can be pretty cheap. I'd do bbq chicken. That way there's no expectations of bread/buns as with hamburgers and hot dogs, and it's less expensive than steak. Maybe an option between chicken thighs and pork chops?
Sides are easy. Grilled veggies rock. Piles of grilled carrots, onions, eggplant, mushrooms. Kabobs are always an option. You could even do cold kabobs made of cherry tomatoes, cheese cubes, and other raw veggies, and marinate them.
A fruit tray always seems to get a good response, or any variety of fresh fruit in a large bowl.
Zucchini hummus to dip raw veggies in? Or maybe guacamole?
Cabbage is pretty cheap, so you could make coleslaw as a side dish.
Devilled eggs of course.
Dessert could be just berries n cream like I plan to have (and it's pretty red, white and blue) or you can do coconut milk custards. Those are pretty cheap to make and taste totally YUM. Then put a few raspberries and blueberries on top to make them festive!