Start working it out at your grocery store. It's not as easy as it looks.

I'm not saying it is impossible, far from it, but you do have to be conscious of every single purchase. That head of broccoli is $2 this week? Maybe not in the budget. Apples are up to $1/each again, those are right out. These aren't crazy organic prices either, this is regular produce and store brands. This goes double if you're trying to eat a healthy balanced diet and not going for a college kid ramen diet.

Even worse with a budget so small it is hard to take advantage of buying in bulk to save money. Buy a 50lb sack of potatoes and you can't afford to each much of anything else for the week. Buying flour to make bread is a great cost saver when you are buying in 40lb bags, but not so great in the 5lb bags with the markup.