Hey dude, as a long distance backpacker and someone who grew up poor, I have some ideas for ya.

Tortillas are a staple, plenty of fat and good calorie count. If you can stomach tuna, I recommend making a big bowl of tuna salad. Large can is pretty cheap, you can also buy single stalks of celery at Kroger(because who tf eats a whole bag of that stuff??) not sure where you are but Safeway and Vons are both affiliates of Kroger. That will take care of your lunch, throw it on the tortillas with your choice of chips(do this every other day so you don’t get bored of the textures)

You can also throw pb and a banana on the tortillas for breakfast, bonus points if you heat it up on a skillet)

I’d buy the big long thing of chicken tenderloins or breasts, whatever is cheaper and a few veggies. (Peppers, onion, peas) stir fry mixes are decent and cheap but fresh would probably yield more bounty.

Cut and cook your chicken up, alongside a big bowl of rice. Add whatever veggies you feel like for the day. (Also dank on a tortilla) this got me through weeeeks of college and fed lots of friends when I had to throw meals together.

Don’t be afraid of salad! If you buy purple cabbage and char or mustard greens, that stuff lasts sooooo much longer than bagged salad.

Not sure if you’re familiar with Knorrs “pasta sides” but they have some delicious combos that you really wouldn’t need to add anything to, although tuna goes great with a lot of them(that’s the backpacker coming out) especially if you’re eating alone, they make a good amount of food for the one package.

There’s always ramen. The calories are there and it’s so easy to spice it up with some green onion and sriracha. (Also tuna lol) Throw a hard boiled egg in the mix and you’re golden.

Good luck mate! Eating while poor is totally possible.