Some of my favorite easy and fast foods/snacks for $5 or less that aren't ramen and spaghetti:
Couscous. You can get boxed couscous for like $3 and it's enough for 2-3 side dishes at least and takes literally 5 minutes and no extra ingredients. You can get large containers of it for like $5 at Walmart too so you can season however you want. A nice grain that's easy to digest and pairs well with almost anything.
Popcorn. Everyone's favorite healthy junk food that can satisfy most cravings. You can usually get a box for like $4 or a jar of kernels for like $6.
Oats. Whole oats. Extremely versatile. Put them in smoothies, make cookies, granola, snack bars/balls, brownies, oatmeal, etc. Truly the best bland fiber and filler out there. You can even easily make your own oatmilk for super cheap by blending them with water and straining!
Frozen veggies. Last for months in the freezer and usually under $2 a bag. Not great if you prefer raw veggies, but if you are fond of sautéed or roasted ones, save some money and just get them frozen.
Chocolate chips. Cheaper than chocolate bars and you get a lot more chocolate. Perfect for those cravings!
Powdered potatoes. I know I know but if you ignore the package directions and put some butter and milk and seasonings in it, you can't tell. Ready in like 2 minutes and you get a shit ton of mashed potatoes for like $2.
Vegan Mac and cheese. I'm lactose intolerant and so I will forever be thankful for the vegan movement of the early 2010s for making nondairy products easier to find and more affordable. Vegan Mac and cheese literally tastes the exact same and bakes so well. Annie's so far has been my favorite brand and they have other pastas with sauces too like squash which is so good.
Crepes. You can make your own batter for cheap but who likes all them dishes? You can find pre-made crepes for like $3 for 10.
Apples. You can find 2lb bags of these for $3 at a lot of places. I never knew they were so cheap and I go through phases where I'll eat like 4 a day.
Lunch meat. Packs of turkey cost like $4. I use turkey on so much. Bagels, omelets, salads, sandwiches, wraps, croissants, etc.
Ready to bake pastries. I'm not a big bread person but croissants ready to bake have my whole heart and cinnamon rolls can really help make a bad day a little better.
Pretzels. I'm an absolute whore for Pretzels and eat so many of these things. They're so easy to pack for snacks for class or anything really. I can't go two weeks without them.
Rice crisps. Rice cakes are great but they're big and crumbly and get stale if you don't close the bag JUST right. But little Rice crisps??? Elite. They come in so many flavors and are super crunchy and they're just super cute too and they're bogo a lot at publix.
Frozen potstickers. You can get them for so cheap and I have a giant bag of them in my freezer right now that I got for like $7. I usually get smaller portions for $4 or so though but decided to splurge and get 3lbs of them cus why not.
Frozen shrimp. A bag of extra small Frozen shrimp is about $5 at Walmart. Eat them thawed and cold or put them in pastas or rice or Soups. They're a staple in my house.
These are just a few I could think of off the top of my head. Please add to the list!