Find a grocery store with a good bulk section. The grains you can buy there are a good source of vitamins, especially the B vitamins, fiber, and some protein. We’ve found that we really like porridge made out of wheat berries instead of oats. Just a personal preference.
I second Dangerosa’s suggestion of finding an Asian market. They definitely have rice cheaper than the regular grocery store, and around here at least, they have spices and fresh veggies cheaper than other stores.
Homemade spaghetti sauce is cheap, easy and filling. Look for sales on either bulk sausage or ground beef (or both) and canned tomatoes. Cook the meat with some garlic and onion powder. Add in the tomatoes (I like a mix of diced and crushed tomatoes but see what’s available and cheap.) and add salt & pepper to taste. If you have it or can afford it one or more of the following spices are good: oregano, basil, thyme, marjoram. This freezes really well (but freeze the sauce alone and cook up spaghetti when you want to serve it. The pasta doesn’t generally freeze very well.) and reheats really quickly.
Homemade chili. I don’t have a recipe, but again, find ground beef and canned tomatoes on sale. Beans are cheap and a good source of protein and fiber. Plus chili is usually filling/satisfying, especially during the winter.
Homemade soups. They’re a great way to use frozen/canned vegetables, which are generally cheaper than fresh and sometimes have more vitamins (because they’re picked when they’re ripe, not picked while they’re green and forced to “ripen” on a truck. Plus they’re immediately frozen or canned so they retain more vitamins than those that have to travel a long distance to get to a store. I don’t have a cite at the moment but I could find one if you want.). And soup can stretch a small amount of meat over many meals.
If you have one, pull out you crock pot/slow cooker. The tougher cuts of meat tend to be cheaper, and if you cook them all day in the slow cooker, they turn out falling-off-the-bone tender. Pot roast and stew are great. Note though that it’s generally cheaper to buy a roast and cut it into stew-sized chunks than to buy the pre-cut “stew beef” but check the store and see what’s a good deal. Again, these are hearty meals that keep you full.
It takes time and effort, but the best way to cut spending is to price compare. Look through the ads, look in the stores. Keep a list of what costs what so you know when something’s a good deal. (I can’t keep the prices for everything we buy in my head, but if you can, you don’t have to have a list.) Just because it’s a store brand doesn’t necessarily mean it’s cheap. Look at the prices, especially the unit price. Similarly, just because it’s on “sale” doesn’t mean it’s a good deal. This is where having a list of the things you frequently buy and their normal prices really comes in handy.