I make as much of my own food as possible. So I mostly buy basic ingredients.
Mayo, ketchup, BBQ sauce, ramen broth, grow my own yeast, bake breads all types, pizza dough for home made pizza, kimchi, grow some herbs and other plants when possible. You eat healthier, and tastes way, way better. Some planning required since you make things in bulk but since there are no preservatives, food will not last months, unless you also make your own preserves, but it gets easier with practice. Pickled stuff is delicious.
Also, will buy meat with bone in, use the bones to make broth and sauces for better for flavour.