GOTTA EAT BIG TO GET BIG, BOI
You should eat a chicken a day if you can afford at least $5 for food a day. That'll get you like 3-5pounds of chicken at about 300grams of protein. Then fill yourself up with carbs, veggies, protein smoothies made with peanut butter - and don't forget your fruit. Or you can just do chicken, a multivitamin, and some peanut butter based smoothies with whole milk. Don't forget your eggs. Get you the cheap pasta.