As far a cheap food, a big pot of veggie chili is cheap! And actually pretty healthy. 1 dozen eggs will give you 2 eggs a day for breakfast for 6 days. A big container of oatmeal from walmart, breakfast for weeks. Big bags of frozen veggies from places like walmart, are also cheap.
One thing I found at walmart, the fresh chicken breasts in the big packages, while they seem expensive, about $13, they are big enough you can cut them in half and they are about the right serving, so one package will make about 20 meals of chicken breast.
And my latest fave. Pizza soup, 1 little can of sliced mushrooms, 1 serving of Candian bacon, a generous sprinkle of oregano and top with tomato juice and a bit of mozzerella cheese. Yummy! Pizza without the fat.
You can bake or crockpot one whole chicken and have chicken burritos, chicken salad, chop it up and have chicken sandwiches.
Explore your local groceries, ask them when the best sales are, especially for fresh stuff going out of date soon.
I know you are busy, we all are. But just a bit of time dedicated to food will pay off in the long run.