First off, you can make your own bread and reduce that $5 frozen pizza to a $3 fresh pizza with whatever ingredients you want on it.
You can start by making a budget and watching what exactly you are buying, then tweaking that until you are happy with the financial to taste ratio (such as, not buying pop, or buying half as much).
Planning meals in advance makes it easy to purchase only the things you need. Cooking from whole fresh ingredients is more healthy and more tasty in my opinion than buying frozen premade foods. Similarly, buying fresh foods is often cheaper, here here in Ontario only one of the two taxes are applied to fresh foods, compared to frozen foods which get both taxes applied.
Buying in bulk also reduces your prices.
Never buy hummus. My god, it’s one of the biggest markups I’ve ever seen! Even buying a can of soaked chickpeas is on the higher price of things – if you buy dried beans in bulk, soak them the night before, then throw them into a food processor or blender, you have reduced the costs from $3–4 for a premade thing of hummus to 25, 50 cents for at least twice the volume of hummus. Multiply this by everything you do and eat and you can see how to save a lot of money – buy bulk, make it yourself, and don’t eat too much of it.
I am currently investing money in high quality (restaurant grade) food storage bins for my pantry, in which I put my bulk purchases of flour, sugar, oats, etc. One problem you can encounter when buying bulk is little bugs and pests, so it’s important to eliminate the chances of contamination. A cool trick is to throw your stuff in the freezer for a few days which tends to kill most if not all pests that may exist.
So to solve the issue of not knowing what to buy, you need to plan your meals in advance. This can actually be relaxing because then you know what you are making for dinner and who can do what. Plus you can have something to look forward to during the day! Lunches can usually be the leftovers from the night or two before. Cooking saves money but takes time, it’s a careful balance, but I promise you it is well worth investing time to learn how to cook and bake your own foods. Cooking from actual ingredients versus popping a precooked item in the oven will produce a more nutritious meal with far less junk and fatty crap. And try to save at least one portion for a lunch the next day, because it’s a sure thing that eating less food will cause you to spend less money on food.