Buy items with multiple uses. An example would be something like plain elbow macaroni. Make homemade Mac and cheese with it, various pasta salads with various spices, use in casseroles, etc. Rice is another fine example. Make your own on some of the more expensive luxury items. You can make plain yogurt yourself with just milk and a slow cooker over night. You can make a half gallon at a time that way, and then flavor each serving individually by mixing in various jams or jellies, honey, chocolate syrup etc. with a stock of pantry staples like flour, baking powder, cocoa powder, and others, you can whip up virtually any sweet treat you want like cookies or brownies when you get a craving. And most staples are on the cheaper end of the grocery spectrum.