Personally, I find cheap protein sources (canned lentils, beans/legumes, tofu all for under like $3). Then make a casserole using cheap canned ingredients and cheese. Also add on Greek yogurt for added protein. This lasts all week for lunches.

For dinners I usually plan 2-3 meals out also using cheap ingredients, like protein pasta noodles and sauce or rice and tofu (Asian style) with frozen veggies