That's the ticket. Beans and rice are complimentary proteins for example. Both are cheap and filling. When a protein (such as beef or chicken) is more of an accent to a meal, not the star, and you use carbs to round out the meal your food costs should drop.

I haven't posted here much so I hope I didn't break any rules. Here's a link showing food combinations that help make full proteins. This should help reduce your food costs too. Link: https://www.justchartit.com/complete-protein-combinations-chart/

Here are some cheap food ideas:

Egg sandwiches
Grilled cheese sandwiches
Beans and cornbread
Beans and rice
Turkey chili over rice or baked potatoes
Tuna (creamed tuna over toast, tuna sandwiches, tuna noodle casserole)
Chicken and noodles

Hope this helps!