I eat a pretty much gluten-free diet based off of Justin Lascek's recommendations in his great book Paleo for Lifters
http://70sbig.com/blog/2013/07/paleo-for-lifters-qa/. I eat what most people would consider a lot of food (~4,000 calories a day).
Basic summary is meat, eggs, more meat, potatoes, white rice, vegetables; don't forget to kill everything with olive oil and butter. I am throwing in whole milk for more easy, cheap calories as dairy doesn't bother me.
Here is what I eat pretty much every day (not a picky eater):
Breakfast: 6 eggs with spinach, hash browns with butter. ~$0.75 for ~800 cal
Lunch: Two chicken thighs topped with olive oil, cup of white rice with butter ~$1.25 for ~960 cal
Dinner: Pound of ground beef, mashed potatoes with butter, frozen broccoli ~$4 for ~1400 cal
Snacks: Maybe a pint of milk and .5 cup nuts. ~$0.80 for ~700 cal
That's about 4000 cal for $7. This reminds me that I need to go eat.