Beans. No need to fool with dried beans, unless you want. Drained and rinsed canned beans are economical and almost ready-to-eat. Low fat, too.
Greens. I'm all about the instant gratification, so I usually buy frozen. Still cheap. Non-existent fat.
Cheaper cuts of meat (chicken thighs, round steak) that you can cook in a slow cooker. Not the lowest of the low fat, but usually economical. Internet recipes abound, but be careful of the overuse of cream-of-crap soups, cheese, and sour cream.
Combining a box of thawed greens (squeezed dry), a chopped/sauteed onion, a can of drained and rinsed beans, a bit of chopped leftover meat, and maybe a sweet potato makes a mighty fine meal.
Example 1: mustard greens, black-eyed peas, onion, chopped ham/Canadian bacon, and sweet potato.
Example 2: white beans, kale, onion, handful of dried cranberries, handful of chopped cashews (a 99-cent snack size bag from Walgreens does the trick). No meat needed.
Example 3: Drained, rinsed and dried chickpeas roasted in a little olive oil until brown and crispy. Season either sweet or salty, as you wish, and snack away.
