You asked what meal, and I'm going to answer that. But first: bananas. I eat 3-6 lbs. a week.
Meal: hummus, falafel, lentil soup
I shit like a pro afterwards. Cheap, easy to find ingredients. When I learned to make those three and make them well (I had to ignore virtually every recipe I found), it was like..."I know Kung Fu."
Truly a worthwhile thing to know how to do if you want to eat healthy and still taste food. A lot of people on /ck/ think Middle Eastern food is shit tier, but whatever.