I always add some brown rice and bran when I make food for one of my dogs. In the wild a dog will eat anything. However, I never add any wheat or corn-based ingredients as they're used simply as filler in many commercial foods.

One very important item to note, read online and also mentioned by a retired vet friend, is to make sure you are adding vitamins/minerals to the food you make, because the ingredients you're using may not contain enough of what your dog will require.

Bone meal, and fish oil come highly recommended. If you're making a batch of food, freeze it, don't just keep it in the fridge if it's supposed to last more than 3 or 4 days.

Oh and from the vet friend, garlic is good, onions not.