I understand your concern; I make far less than minimum wage and don’t have much money to spend on food. Although I love to cook, I barely have time for it, so I generally only do it on weekends. I’ll make a huge amount of vegetable-laden rice and beans, or pasta sauce with vegetables and a protein source in it (I’m vegetarian), or lentils, soup, a Spanish omelette, casserole, or collards or kale, or various stir fries or curries, etc. (I’d be glad to provide my version of any of these recipes if you are interested). Then I’ll freeze ¼ to ½ of it, so I don’t have more than I can eat fresh (and then I can always defrost these things later when I am feeling too lazy or busy to cook!), and then I eat the rest of what I have throughout the week, for lunch and dinner. Tupperware is your friend!
The way to keep your groceries bill down is to buy basic ingredients as much as possible. With prepackaged food, you pay for convenience and (yuck) processing. Also, try to stick to store brands of everything. You can often find coupons for the store brands, too.
Here is a schematic version of my weekly grocery run:
-1–2 kinds of fresh fruit, whatever is cheapest per volume (sometimes I can even find buy one get one deals)
-1–2 sources of protein (dried beans/lentils and eggs are the cheapest, peanut butter is good too, sometimes you can find yogurt for real cheap as well)
-2–3 vegetables (spinach for salads, a head of broccoli to steam and eat through the week, kale, a sweet onion, a can of chopped raw tomatoes in juice, etc.)
-1–3 kinds of starch (usually pasta or egg noodles-store brand is SUPER cheap!, whole wheat bread, not as cheap but much more nutritious than crappy white refined bread, potatoes, tortillas or taco shells).
One of the keys to being able to cook with a modicum of variety is starting off with a good stock of spices and condiments. You don’t have to try to buy these all at once, but pick up one or two items every time you go shopping. Black pepper, basil, thyme, garlic powder, oregano, paprika, (hot) chili powder, vinegar, mustard, salsa, vegetable or meat boullion, etc. Having versatile ingredients like this ensures that you can always cook something decent at home, no matter what groceries you end up buying for the week (rather than having to go shopping for each individual meal, which is a pain and I don’t really understand why people with refrigerators do that.)
Anyway I’ve gone on a ramble here because I like food. Hope this was helpful.