You can use pretty much anything as a pasta sauce, baked potato filling, pizza topping or pie filling. We had slow cooked belly pork with apple juice and onions served with veg for Sunday dinner, and there's plenty left to cook up with mushrooms, peas and a splash of cream to use as a pasta sauce for tonight.
Asian grocers are great for bulk buying lentils, chick peas, rice etc, and sell spices and gram flour for a really good price.
We generally try and do a pasta meal, rice meal, soup meal, pastry meal every week.
Things like shakshuka with crusty bread are quick and cheap, veggie quiches, pasta sauce with an inch of chorizo chopped small and fried with garlic and onion, then add some roasted red peppers, mushrooms and tinned tomatoes, chilli or herbs.