My dog eats either Wellness brand kibble or our homemade food for her consisting of any combination of these:
poultry
salmon
green veg (broccoli, spinach, kale, green beans - she will eat those all day)
yam or other potato
oil (olive, fish, flax)
grains (oat, quinoa, millet, brown rice, a little ground flaxseed)
...in that order. Easy on the carbs; about 1/8 is grain. My recipe has a lot of fat, but it's for active dogs in cold weather. I cook it all in a batch and freeze portions in ice cube trays or other containers. Some people don't like any grains for dogs, and some only feed raw food. But for my dogs this has been fine (Boxer and Dalmatian, lean and not-so-mean agility and running athletes). It's fairly cheap too.
I also add MSM for joint health.
And if he won't eat that, try ground lamb in some of it. I think it's gross, but I've never seen a dog turn down stinky fish or lamb! Or yogurt. Dairy isn't supposed to be part of a dog's diet, but mine have always thrived with a little yogurt now and then.
And one more thing...he won't starve himself long. If he doesn't like any of the suggestions in these answers, he may have stomach issues the vet could help with.
