+1 for PrusaSlicer. It’s great and I like it’s tools for minimal editing of parts: cutting, placing and scaling…

You can get nutrients from the sauce. IMO tomato sauce is very tasty and can be pretty cheap as well. Probably the cheapest would be tomato paste and water as a base. Or canned tomatoes. Depending on how cheap you want to go you can add vegetables to your liking. Onions are always great but also carrots or peas.