My staple go to veg is frozen stew packs from farm foods. They are 5 for £4. Onions, carrots, celery, Swede .
Add one, steering steak and spuds =stew/Scouse.
Add one, a small £3 gammon joint /£2 streaky bacon and a bag of split peas = peas and ham soup.
Add one and some leeks, diced potato and chicken stock/scraps = leek and potato soup.
I use one to pack out my Bolognaise £2 mince and pasata, and the veg renders down and makes a really deep flavoured pasta sauce.
Otherwise I do a very basic pasata based sauce with Tom paste, basil , oregano and a half tsp of sugar. You can chop up hot dogs and then mix it with pasta.
For a easy cheat sauce you can top a tub of cream cheese into a pan of drained pasta then add chopped ham or peas.
Sausage and beans on toast with cheese.
Toastie and soup.