Let's just say that my experimentation with bread and sourdough wasn't simply for the joy of cooking (though that was a large part of it). All told, I'm not sure homemade bread is much cheaper than the low-end storebought stuff, but it tastes scads better.
Minimally processed foods in general are your best calorie|nutritional value for the buck. Rice, beans, canned tomatos, and a healthy selection of spices, with the odd bit of meat tossed in for flavor got me a long ways. Pasta. Make frugal dining a family game. I note that (on the few occasions I do shop at a "discount card" store) my savings on a $75-$100 purchase are rarely more than a dollar or two. The discounted items are usually in the processed/prepared food category. I don't buy that crud.
Odd note. Two of my food addictions are directly attributable to poor-as-a-dog college days. Grape Nuts (at about $0.13/ounce) are one of the best cereal bargains (in an otherwise expensive food category) and espresso. Plain old coffee doesn't do it for me, and the double-ex was the least expensive of the high-octane boosts I could find. I generally only do two mugs a day, rather than staying on a constant caffeine drip.
Walking or cycling places saves gas, gives exercise, and in my experience does wonders for my sanity.