One of the best dog foods I've used was passed along to me by a kennel owner that raised guide dogs and also kenneled dogs. All dogs seemed to thrive and enjoy this mix:
Inexpensive dry food
A cup or two of milk replacer (calf blend sold at farm stores)
Water
Eggs occasionally
Chopped beef almost daily.
The last two ingredients were tailored to the dog's physique and coat condition. The mix or gravy was not so moist that the dry food was totally saturated, it allowed for some "crunch" so that teeth and gums were involved.