I always cook as much of whatever I'm making as I can, then put it in containers in the fridge or freezer (depending on the dish and how much).

And I have some base recipes that I cook that are easy to quickly make other things with. One thing I've done for almost two decades now is make a basic kinda "half-bolognese" (can't think of a better English description right now). Just onion, garlic, meat (or in my case vegan alternative), salt, pepper and some stock of your choice. Then freeze that divided into a couple of portions per bag or container. Very easy to use for a lot of recipes.

I also buy bags of dried beans (way cheaper than undried or pre-soaked) and soak those then freeze them like above, same thing there with being good bases for many things.

One of my current favourite recipe that's quick, cheap and filling without any of the above prep is falafel in tomato sauce. A local brand here in Sweden makes almost weirdly nice falafel that's $5 for 800g (28oz), which is like 50 falafel balls. I put the falafel in my air-fryer (oven or frying pan works just as well) and while those cook I sauté some onion and garlic in olive oil then add spices (the current version I love is with some smoked paprika, cumin, oregano, thyme, black pepper, lots of turmeric, a bit of soy sauce, a stock cube and either MSG or other umami base). Then add the falafel once done and crushed tomatoes and let cook for a few minutes. Works great with rice, pasta, potatoes in whatever variation you like, couscous, and my current fav which is coarse bulgur with vermicelli (roasted noodles). I wouldn't have guessed it before trying but the falafel is so good in the sauce!