I second the Mexican grocery stores as well as other ethnic shops. You can get great cheap produce as well as stocking up on bulk items.
I recommend making a big pot of soup and then supplementing that with various salads/sandwiches/flatbreads throughout the week. It'll switch it up just enough to not make you hate your life on day 5.
I have been making a slow cooker full of chicken breasts or thighs cooked with cumin, chili powder, garlic, cayenne pepper, jalapenos, etc. and then shredding the chicken, adding black beans and using it for taco/enchilada filling, salad topper, etc. It's easy, relatively cheap and useful in a lot of different ways.
If you want to eat out, hit happy hours or lunches. You can pick up those Restaurant.com GCs for 80% off at least once a week, but there is usually a minimum purchase so it may not be the most budget-friendly option.