When I was single, I spent the same amount on eating out as I did on Groceries. About $1,300 each per YEAR, or $120 a month each. Most store brands were as good as the name brands, so save money there.
Breakfast was cereal that was on sale. $2 box of cereal is 6+ meals. So maybe $0.40 per meal including milk.
Lunch was a sandwich, some chips, fruit, a coke, and some cookies. Bread is 10 cents, slice of meat and cheese $.75, coke is 0.33, 0.35 for fruit, and cookies are 0.20. So about $1.73 for lunch. Way cheaper for PB&J.
For dinner, pasta, rice, and potatoes are really cheap. 25 cents per serving or less usually. Butter, and spices are cheap. Vegetables are cheap. Add some cheese and you're good. Ground beef in a tube is cheap. Whole uncooked chicken is cheap and 4+ meals. Make 3 or 4 meals at a time, and then eat left overs. About half my dinners have meat, half do not. Meals without meat are usually about $0.75. With meat are about $2.5. They probably average about $2. Learn how to season with salt, pepper, and garlic, and and almost anything will taste good.
$1 box of brownie mix plus a few eggs is dessert for the week.
I almost never bought anything from the frozen food aisle, or the bakery. Like others have mentioned, I bought whatever meat was on sale.
When I did go out to a restaurant, that was usually 2 meals, I ordered water, never got an appetizer or dessert, and no alcohol. $15 entree + tax and tip is $20.
Oh, and stay single. Girlfriend obliterated my budget since we had to go to nice restaurants and buy name brands. My situation is maybe a little extreme, but I grew up on cheap foods, so that's what I still like.