My general rule is to put planet and people first.

Sometimes I can't afford this (like when I buy plastic rain boots) but I try.

I try to mix this with frugality. Such as buying only natural fiber tops from the Thrift Shop.

Participating in the local Community Supported Agriculture (CSA) helps. The one in my town lets people work for free food if they can't afford the subscription.

Walmart is evil. It does not exist in my mind. That way, no decisions about how close, etc.

Cutting out gluten has really saved me from lots of low-nutrition carbs and $4 loaves of whole wheat bread. I have more energy when I eat just protein and produce.

Vitamins are important. I went to a nutritionist who had me get a blood test. The results told her exactly what vitamins and supplements I needed and which foods to avoid. (Starch is especially bad for my sciatica. 1 year of no starch and I am pain free.) She sells them to me at her cost plus 10%. I feel great and saved money on sciatica Rx and doctor visits.

You can eat cheaply on lots of carbs (rice, wheat, corn) and starch (potatoes, sugar) but it's bad for your body. Protein and produce. Eggs and tofu are cheap.

Good luck, OP!