Follow this formula:
Protein + veggies + carb.
Cook the protein first, add the veggies, and serve it over the carb. Vary the seasonings or find some inexpensive prepackaged or jarred sauces you can add.
For instance, chicken thighs with carrots and red onion served with fingerling potatoes. Pork sausage browned with yellow onion and braised cabbage with rice. Pork chops with onion and apples and spaghetti squash.
Vegetables - especially root vegetables - are cheap. Ask you grocer when they usually put their meat on sale and purchase your meat then. I've recently purchased packs of 20 oz of pork sausage for $1.49, 14.75 oz cans of salmon for $3 (100g of protein per can), and a 33 oz pork shoulder for $5.99.
For breakfast eggs, oats, and sausages are your friend. Don't forget to eat plenty of greens for fiber.