If you're a veggie, an easy dish to make is pasta (penne) with tomato, spinach and onions and mushrooms. Courgettes can be added as well.
Chop up some garlic, and heat up some olive oil in a big frying pan (or any kind of pan). Fry the garlic for 30 seconds - 1 min, then add the onion and mushrooms (and courgettes). Fry for a few mins, till soften. Roughly chop up some spinch and add to the pan. The spinach will wilt down after a couple of minutes. Add one or two tins of chopped tomatoes. Season with salt and pepper to taste, plus add a few chilli flakes, if you like it spicy. Simmer. Boil your pasta as normal - 8 to 10 mins or til al dente, drain, and add to the pan and mix it all together. Remove from heat, and serve with grated cheese, and maybe some bread, preferably garlic bread. Whole thing should be relatively cheap, plus you can make lots and fridge it for a couple of days.