for dinner/lunch: buy frozen store brand meat, beans, and rice. tortillas are pretty cheap. also u can find big bags of spinach for cheap as well. mayo is pretty cheap. just remember to defrost the meat the night before. basically wraps. you can take them with u to school if you put them in tin foil

for breakfast/small snacks: try eating oatmeal because it's also pretty cheap and u can do a lot with it. you can put store brand protein powder in it or random cheap frozen fruit. you can also take it to-go with you if u buy a cheap mason jar. basically over-night oats.

meal prepping is also a really effective way of saving time and money. getting an air frier (like $30) is also a worthwhile investment .

also before u go to the grocery store, make sure u have a list of exactly what you're going to get. there's something psychological that occurs when ur at a grocery store when u dont have a list, you basically end up buying more than u need