Well, you can also get lentils, whole-grain bread/noodles/rice/flour, chickpeas and other things as cheap staples (if one leaves the meat out as in my example it's not even optional), but I guess that's not what you mean? What would be your suggestion as staple?

There's a problem with nutrition research in that it changes recommendations every once in a while. The only constant seems to be 'Eat food, mix it up - naturally colourful things are good, don't eat too much of it', so I'm going with that for now.

Concerning time.. it's maybe more of a knowledge and organisation thing, which takes time to aquire. Unless you want really fancy food like sushi.