I'm know I'm repeating some suggestions, but these are the sorts of things I would do:
A tin of the cheapest tomatoes with herbs and spices makes a cheap pasta sauce. Add a bit of finely chopped onion if you have some and anything else .
Not sure if you eat eggs, they are nutritious and if the main part of your mea, quite cheap. Spread out over the weeks for variety.: 2 boiled eggs; 2 egg omelette; 2 scrambled.
I'd make a vat of lentil soup. If you've a freezer, freeze in portions so you can spread out. Otherwise it will keep for a few days in the fridge, a little boring if you have to have it each day but filling and nutritious.
1/2 tin beans on toast one day & the other half on a jacket potato the next.
If you can get a Lidl veg box, make a vegetable risotto, vegetable stew, vegetable soup, veg stir fry (if you have soy sauce in your cupboard, that is enough for a stir fry, you don't need to buy a sauce) .
If you get aubergines and/or courgettes in the veg box, you can add tinned tomatoes tk make ratatouille. Appreciate that might be too expensive if you can't get the veg cheaply.
If you have curry powder, fry a bit of onion, add some curry powder, add a portion of rice and slowly add water/stock til cooked. I used to eat that on its own when I was a student but you can have it as a side too.
If you're happy to, keep track of what you eat and create a post as I'm sure lots of other people will be interested.