Potatoes: Peel and cut up potatoes. About one or two medium potatoes per person. Now put the potatoes in a pan, cover with water or other liquid, and boil until they are very soft. Drain. Mash or put through a ricer, add milk and butter.
Gravy: Make a white sauce (see my source), and instead of the milk or cream, use chicken or beef broth (depending on what you're serving). Or just make the white sauce, and season well with salt and pepper. Or you can make white sauce, but add a chicken or beef bullion cube or paste.
If I am making something like chicken fried steak, I use some of the fat from cooking the steaks as the fat for the gravy, though this doesn't make a true white sauce.
When making gravy, you really have to stir and stir and stir, not just when you're cooking the fat and flour, but after you add the liquid to it, too.
If you want to cheat, you can use a can of cream of mushroom soup, heated, for the gravy.