Well, I've found that it takes a lot of extra money (and time!) to worry about hitting all of the food groups in each meal. With my little ones (4,2, and 6 months) underfoot, I don't have a lot of time for the kitchen. Well, I suppose I could carve it out, but...
Anyway, we rotate oatmeal, eggs, cereal or bread (think muffins, etc) for breakfasts. Saturdays my dh might make pancakes with the kids. Or, if we are feeling particularly awful, we might get donuts. Sundays I might make overnight french toast, or apple crisp the night before. Or, we have oatmeal again.
For lunch we rotate potatoes (sweet, white, or red, usually baked, sometimes seasoned), rice, and bread.
We snack on whatever fruits and veggies were cheap. Maybe some nuts and cheese. You can also sneak in a bit more nutrition by finely chopping whatever meat and veggies and cheese you have leftover and throwing them in with the rice or eggs or whatever.
Then, I cook a real supper with rotating recipes from my menu.
Doing things this way keeps me from being a slave to the kitchen, while allowing us to still eat a "real meal" once a day. It also saves money because I'm not buying all sorts of extra ingredients to make a bunch of different meals. One bag each of potatoes, rice, oatmeal and 2 dozen eggs cost roughly $10 and feed us 8 meals. Oh, did I mention that simple meals are also easy/quick to clean up?
Another thing that makes meat go a lot farther is to cook it whole, and then cut it up. My dh can eat half a chicken in one meal. That's expensive! So, I rarely do that. I cook the whole thing (usually boil it, so I have broth), and cut it up. Then I can throw a handful into lots of dishes. Yes, we are eating less meat, but really no less that we NEED anyway.