The same triple constraint nature of the project management triangle exists, I think, with food intake. Quality, cost, and ease/speed of preparation -- pick two.

Every two days, I cook up 2 lbs ground beef, boil 4 cups beans, and 4 cups rice. I let it cool off, and throw it in Tupperware, and into the fridge. I take from that whenever I'm hungry. It doesn't taste the best, but it fills you up, is cheap, and is good for you! If you're feeling the need for some extra veggies/fruit, avocado, frozen blueberries, and frozen kale offer the most nutritional content at the lowest price and least preparation time.

Like work, I don't think this will ever be 'optimal', but it's good for now, in that it saves me time, money, and waistline. Can tweak it as I go.