Cook your own food. Ready made meals will always be made with as much cheap non nutritional filler as possible. Learn how to use a few spices, buy produce that is cheap with the season and keep track of weekly discounts in your local stores. It will save you money, you'll eat better and it's rewarding to have a tasty meal in the end.
Also I'm surprised how many people don't seem to understand pricing in general. When comparing prices, see the price per weight or volume. That is money/kilogram or money/liter (substitute with freedom units). Money per package can be deceiving if you compare 75 money for a smaller package or 95 money for a larger.
Edit: If the need to learn spices makes you overwhelmed, start out with some spice mixes! Pick a couple of different blends that are different, like one Cajun Mix and one Mediterranean and one oh idk something else culturally generic. Also salt, pepper, paprika and bullion. There. You can make lots of different sorts of foods and learn on the way what spices you like. Don't be afraid to experiment. Don't get discouraged. Some stuff will turn out meh, but others will make you go wow. All of those are learning experiences for the future!
On the cooking one, I also recommend cooking double portions when you can. If you can cook twice as much with minimal effort, that's half the cleaning you have to do afterwards and half the meal planning you have to do. You get up in the morning and know that you have leftovers from dinner ready to go for lunch in the fridge. Also, rice. Rice is cheap, good for you, and incredibly flexible in what you can do with it. A rice cooker is also a great appliance to have in general. Not only is it an easy set and forget for a pot of rice, but you can do all sorts of meals in it from steaming meats and vegetables to cooking soups and even baking desserts. An air fryer is similarly flexible and great for making meals for one person. You don't have to preheat it or anything and it doesn't cost all the energy that a full size oven does.
That's true. Food prep is great for the economy and also for the soul. You can generally find larger amounts cheaper per weight and it's nice to know them you get home and are tired that there is some good food waiting to be reheated.