For pesto, you can use walnuts instead of pine-nuts, which can make it cheaper. The cheese is the last thing added, so you can keep some back for a vegan version.
For vegan sauce, I'd go with canned tomatoes and make my own, as I think natural flavours aren't usually added to the canned ones. For a simple marinara, use big cans of tomatoes, diced onions, garlic and herbs. For a more complicated sauce, add finely diced carrots, celery and onions, and for a meat sauce, start with sauteed ground beef or pork.