assume you have access to a fridge/oven/microwave and all that
- eggs! / you can make tons of different things with eggs, scrambled, add a hard boiled to salads, frittata, etc. i definitely always keep them around.
- whole wheat pasta / endless combinations
- brown rice / you can make stir fry, add it to soup, stuff it into a pepper, etc.
- canned tuna packed in water
- beans (especially dry beans because there’s less sodium)
- oatmeal / super filling and cheap. you get a lot of servings in a bag! try to just buy a plain bag of oats rather then those single serving microwave packages. it’s cheaper to do that.
- potatoes / cheap, easy to make and there’s a lot of ways to enjoy them. sweet potatoes are the best!
- spinach or kale / i don’t know how cheap this is.. depending on where you are i suppose. i can get them pretty cheap where i live though. really healthy and healthier for salads than romaine!
- peanut butter / good fat and you can do a lot with it.
- raw nuts / sometimes they can be expensive but sometimes i find a really good price on them
- broccoli / it’s usually around $1.50 a bunch here and i’ll use it for stir fry or i’ll roast it.
- now that fall is here squashes and pumpkins! / baking with pumpkin is delicious and amazingly healthy. butternut squash is my favourite and you can get a lot of servings out of them. spaghetti squash is awesome for making “spaghetti” with (http://www.thekitchn.com/recipespaghetti-12975)

i hope this is somewhat helpful. junk food may LOOK cheaper but you get a lot more for your money when you buy healthy foods (nutrition and taste wise).