Typically in a month I'll buy:
Dried Beans
Rice
Pasta
Canned Sauce
Yogurt
Assorted fruits & vegetables
Hummus
Bagels
Tofu
Bocca burgers/veggie dogs/some other meat substitute
Bread appropriate to the fake meat I buy
Triscuits
There are some things I buy less frequently, like olive oil, almonds, mustard, pickles, etc.
Last night, for example, I bought fake meat crumbles, and a jar of marinara sauce. 6 servings per package for each. I cooked the meat crumbles, mixed them with the sauce, and added 1 serving of pasta. The meat crumbles + sauce cost $7 combined. Spaghetti cost $2.50 for 8 servings. So I have 6 frozen lunches for <$1.50 a pop. I also do stirfry w/ tofu and vegetables and freeze that for a similar price per lunch.
I spend more if I eat a lot of Bocca burgers or the like for dinner, but a lot less when I'm cooking with dried beans or lentils. I also grow herbs in the kitchen and get free vegetables from my roommate's plot at the community garden. I'll probably get my own plot next year.