Add chili to the macaroni and heese rather than just hamburger. You won't regret it.
My favorite "i'm poor but eat good" meal is homemade chicken noodle soup.
Buy a bunch of chicken with the skin on while it's on sale somewhere, take it home and boil it in a *huge* pot of water for 4+ hours. After that, remove the chicken and de-skin it and save it in a container in your fridge. Cover the broth and leave it in your fridge overnight.
The next day, skim all the fat and skin that has formed a sort of crust at the top. This removes most of the grease. After that, whenever you're feeling like cooking, tear your chicken up into little pieces, and chop up assorted vegetables(I personally throw in celery and carrots at the least, maybe add others to try to change things up)and at minimum one full bag of egg noodles. Throw them all in the broth and boil it for maybe 30 minutes. Also make sure to season it to taste, chicken broth with no salt at all tastes pretty bad. The more broth you get, the more cheap filler like vegetables and egg noodles you can add. Done properly, you can eat for several days on $10.
Another good thing to try is to add rice to *anything* rice can go with. It's exceptionally cheap and goes well with tons of stuff. Try some on rice. You can use a lot less of the actual meat while still getting pretty full. Heck, occasionally I just eat a bunch of rice.