I'm a broke college student and I can't afford NS... I usually can't even afford the Lean Cuisines!!
I keep my food budget under control by eating lots of fresh fruits and vegetables (I make a 5 minute trip to the store every 2 or 3 days for fresh produce, but you could just get frozen produce too!). If you just get the produce that's on sale that week, you'll spend way less than buying a lot of prepackaged foods. It's a lot better for your health and for the environment! And back to the college student thing - I have very little free time, but I still cook somewhat. If you don't do it regularly, it's intimidating at first... But just get some lean chicken breast, fish, lots of veggies that you can stir fry, brown rice. You can make lots of soups, too, so you can put everything in the pot and then have soup to eat for the rest of the week.
Even if you can't cook all your meals, even just replacing a few Lean Cuisines a week will help the budget.