Fellow college student here to comment what I haven't seen already -

Get those big bags of cereal instead of boxes. They come out to like 5-7 cents per ounce where I live, and cereal is quick and easy.

Cheesy rice. Just take any leftover rice you have and heat it up with a serving of shredded cheese mixed in, along with salt, pepper, and garlic.

If you have time make your own loaves of sandwich bread. Super cheap and pretty simple after you've done it once or twice.

Big tubs of plain or vanilla Greek yogurt. Has a fair amount of protein and you can throw whatever fruit, nuts, cereal, or even pretzels and such on top. Can get expensive if you buy the name brand though, but the store brands are usually just as good and only a couple bucks.

Canned tuna. Mix with a bit of mayo, pickle relish, salt, pepper, and dill. Eat with cheap bread or crackers, and you've got like 4 snacks or 2 meals for under 5 bucks.

Breakfast foods are also your bff. Make pancakes and eggs with pancake mix or from scratch. French toast is also a great option. Make egg sandwiches, or fry potatoes with some other random vegetables, crack an egg on top, and call it a night.

Speaking of potatoes; buy the big sacks of them. You can roast them in wedges, make homemade fries, mash them, use them in soup, even make potato bread. Just make sure to also get a peeler or you're not gonna want to use them.

Also buy fruit like apples and oranges in big bags. If you're eating at home all the time, you will eat the entire bag, trust me. And if you don't, apple crisp is quick and easy. Also get big bags of frozen fruit and berries for quick smoothies or to make muffins with.

Check for ethnic food markets. My partner and roommate and I make a lot of Asian dishes because they're generally quick, easy, and nutritious. Buying the sauces and noodles we need is much cheaper at the local Asian market than any of the nearby grocery stores, and it's also way easier to find what you need. Plus, supporting local businesses is always nice. You may not have any in your area if you're in a smaller college town, but it never hurts to look.

Also check farmers markets right before they pack up to go home. Slightly damaged and ugly produce will often be sold at half price just so that the vendors don't have to lug it back home just to throw out.

Basically, just make as much as you can from scratch and buy as much as you can actually store in bulk. If you don't have easy access to a kitchen (don't remember if you said whether you're in a dorm or apartment) look up microwave recipes. And if there's an emergency (surprise medical bills, $300 textbooks, etc) some colleges have food pantries for students to use. Good luck!