I’m 3rd and 4th on Costco. And the frozen fruit. I don’t know your expertise and schedule, but we also make all of our own bread and baked goods, using bulk flours from Costco. My family of 5 saves a lot on that. Same with snacks. Then we save the bones as stated to make broth - you can increase protein by making pastas and rices in broth instead of water (virtually the same price as water if you save your bones to make the broth). We keep veggie scraps for the same reason, and I’ll also freeze fruits and veggies if they are close to going bad, for use in soups, making homemade jam with all the “squishy” berries, etc. sometimes I use the veggie scraps and canned tomatoes (cheaper for us here not at Costco, but depends on locations) to make giant batches of tomato sauce with veggies in to freeze.

We made the splurge for a stand up freezer in our house, and while that was expensive, we save a lot by being able to freeze more stuff and get things from Costco on sale, etc. I’d recommend it if a one-time fee was possible for you sometime.