I’d really try to get to a foodbank somehow OP as the prices of basics even are shocking me every time I go shopping - but you already know this. If you could get a big bag full, it might be worth the bus fare?
Breakfast: Porridge with milk and water (all water if you don’t mind the taste) and a banana which are usually reasonable if bought by weight on a market.
Lunch: Batch cooked soup with cheapest vegetables you can find and lentils for a bit of protein.
Dinner:
Rice fried with eggs for protein, peas, onion, sweetcorn - whatever you like.
Pasta and sauce
Pasta with a little bit of oil (preferably olive but any is fine if it’s a little bit) and seasoned well with salt and pepper is okay with some roasted/grilled sliced cherry tomatoes, chopped olives, broccoli - whatever you’ve got.
Jacket potato bought from a veg stall and cheapest beans you can find - I can’t tell the difference between most beans.
If I batch cook something like a chili con carne, while not as obviously cheap and pasta and a sauce, it can last days and is really filling if you can find a good deal on some mince or Quorn mince. Or even do a veg chili with peppers and beans. I’d keep it basic instead of using a complicated recipe. If you don’t have any spice though, instead of buying several CV which could add up, you could get those easy packs which I’ve seen in deals where you can buy a few to keep in your cupboard. I imagine this might be cheaper than getting separate spices.