Lentils. Look up some recipes for dal makhani or similar Indian dishes. May at worst need to sub in coconut milk or oil if they use cream/ghee/etc. but tons of Indian dishes are already vegetarian. Can sub tofu for Paneer as well. It will require some spices to get started, which will be a little expensive if you’ve got nothing. But past that, most Indian dishes are mostly spice in a sauce, not too bad to make just taste as you add spices and add them slowly and keep tasting until it’s good. Recipes will get you in the right ballpark but older spices are more dull so they may need more (or less) depending.

Stir fry is also nice and cheap and easy if you can get veggies at a produce stand it’s typically much cheaper. Cut up whatever veggies you like, fry on high heat in oil, add day old rice from anything else you were cooking before (or noodles from ramen or etc. works as well) and some soy sauce, whatever sweetener you use (honey is normal but just sugar or agave are fine) if you can get fresh ginger and grate that and some garlic in, do that. Protein whatever you have works.