Chicken egg foo young is probably the easiest to make at home. It's really good with leftover rotisserie chicken, or even leftover fried chicken! I've used both. I'd say the other must-use ingredients, as far as veggies are concerned, are scallions and mushrooms. Both are necessary for good flavor, in my opinion.
I prefer a brown gravy. Actually the brown powdered gravy mix you get in the store is the best. Just add soy sauce and maybe a dash of five spice powder, and it's good to go.