Learn to cook meals with cheaper ingredients.
Budget Bytes has already been mentioned, but it won't just give you great recipes, it will help you start recognizing what kind of recipes are cheaper to make.
I built a collection of over 150 recipes with serving costs around $1-2, some of them from Budget Bytes, but many from elsewhere.
Rice and beans is a cliche for a reason though. But that really expands to a huge range of cuisine when you actually conceptualize it as "legumes and grains".
A lot of my meals are extremely flavourful because I use a ton of spices for flavour instead of the typical flavour centers in meals, which are meats and cheeses.
So my step father makes a delicious Irish stew where the bulk of the flavour comes from beef, and I'll make a delicious black bean stew where the bulk of the flavour comes from spices. Both are rich, hearty, and filling, but mine is less than a dollar per serving.
You will find inexpensive, but intensely delicious inexpensive recipes from Indian, African, Asian, Middle Eastern, Mediterranean, Eastern Europe, and Latin America, places where historically there have been large populations of people with not a lot of money.
North American cuisine is based on meat and dairy, so that's why it's so expensive.