It's good you've finally gotten fed up with wasting money on bullsh!t junk.
First, realize junk is not food. They should not share the same sentence.
Second, Cooking for yourself is helpful in every way. You learn different techniques and expand your palette, while relishing the fact you know exactly what's going into your body.
Cheap does not mean bad. Some staples I use every week for work lunch:
Chicken. #1. It's invaluable, it's cheap, and it's so accommodating in various meals and different cooking methods.
Tuna, beef chuck (have your butcher grind a 3-pound chuck for a most excellent burger or for use in low-carb tacos), You can get corned beef for around $2/pound. The uses are limitless.
Start with fresh chicken breasts and watch the last 3 seasons of Top Chef. Not only will you wow yourself with what you're capable of, but the women in your life will be amazingly impressed.