Oh, how well I remember those days! Those are the days to consider soups & sandwiches, or casseroles. So, for the previous week or two, *don't throw out your leftovers*!!! I do know people today who toss out what's left of the meal immediately when the meal is over...they're always broke and hungry before payday. Mostly, they are the young generation just starting out who would like to impress people with their "clean refrigerator"... uh, like a couple of my daughters. (Sorry, kids.)

One daughter who does use most of my old kitchen tricks had a "family" get-together. Several other friends showed up, so what she cooked was a bit short for the crowd. She asked me to look through the 'fridge... there were veggies (like yellow squash) that I grated and added to the slaw. There were leftovers that I added (with her permission) to the main dish. There were veggies I added to her veggies for a colorful mixed dish. There was plenty for everyone, and thankfully there was enough for a couple days' meals for her own family. (I replaced her staples before I left, as mommies generally do.)
Those leftovers do wondrous things with a little imagination... no need for a cookbook. And it saves you more than just pennies.

A SALAD: Shred lettuce and divide among plates. Top with any leftover veggies. A tuna pattie, hamburger pattie, piece of chicken, and/or hard-boiled egg can be sliced or diced and put atop that. Got slightly stale bread? Toast it and cube it for croutons, or cut in triangles and serve it on the side. Add salad dressing. No salad dressing: a bit of mayo, pickle juice or vinegar, a touch of ketchup, a favorite spice, any additional veggies you have handy...put all this in a blender, and add spoonfuls of water to reach desired consistency.
A CASSEROLE: A base of potatoes (you can mix up mashed, boiled, fried), or rice, or pasta. Add veggies and cut up leftover meat. You can add cracker crumbs or day-old bread broken up, over the top. A cup of water with some bouillon dissolved in it, mixed well with a beaten egg. Stir everything together, put in greased or oiled casserole dish, and bake til casserole is "set". (Baking time will depend on how much you're putting together.) Just before you think it's done, you can add cheese over the top; bake til it's melted.
OR SOUP: Take your meats and veggies. If you happen to have an onion, chop it up and throw it in the soup pot. Add water and bouillon (1 tsp or cube per cup of water). You can add a bit of tomato sauce or ketchup, and maybe basil or oregano if you have it. ....Make it fancy: Make a slice of toast for each bowl of soup, cut the toast into rounds. Sprinkle some grated cheese on top. Broil or nuke it just to melt the cheese. Now float the rounds on the soup.
Also, yesterday's pork 'n beans, spaghetti sauce, and sloppy joes make a darn good chili when you add the spicy seasoning to it.

Remember, it all depends on what leftovers you have handy. Yesterday's dish covered with a sauce and maybe a pinch of dried parsley makes it something else.
Tomorrow you can add another veggie or meat, and throw it over rice, and it's a new dish again.
Good luck!