I've certainly done it in the very-broke past (distant past, thank goodness).
A lot of very thick soups were a mainstay - seasonal-only veg, plus lentils, pearl barley, pasta, etc. added. Might add that I still make such soups often in winter - dh loves them!
We weren't veggie or vegan, though, so the cheapest cheese added some first class protein.
If veggie/vegan nowadays I'd look at all the lovely veggie curries/dahl, etc. that can be made quite cheaply - as long as you stick to seasonal veg.
We still rarely waste anything - any waste of food really grieves me - so I am fairly inventive with leftovers, and do usually plan meals 2 or 3 days ahead, so that I know what I need to buy. Not that I'm saying I always stick to my list, especially if there are special offers on anything I know I'm going to use.
What do you think would go well with coasters like this?
Baby Reindeer - anyone watched it?