While Eating Ethically is a hot topic among Unitarian Universalists these days, eating affordably is the priority for many.
Once you’ve gotten past the basics (don’t eat out, cook at home, prepare things from scratch, cut down on meat consumption, eat seasonally), and you find that your grocery bill still could use some trimming, then check out this database of searchable recipes. You can search by price-per-serving, among other factors.
In my mind, eating more simply, closer to the actual natural state of the food itself is ethical eating. Good for the pocketbook, too. How do you balance food budgets and wanting to put your values on your plate?