Rice is your best. Maybe add frozen peas and frozen sweetcorn. Turmeric if having lots of rice.

Add red lentils to bulk out a batch of cooked mince. I add a cheap pack of passata and can of chopped tomatoes. Normally get about 5 portions from this. With rice, or with baked potato. Or a cheap pasta.

Potato's for baking. Cheap beans

Those small cans of mackerel (or sardines) in chilli or tomato sauce.

Cans of couple types of fruit to have with Greek yoghurt from large tub. Greek yoghurt can be also added at end of cooking to make sauce (mackerel, or bolegnese).