i wouldn't buy any dog food from the grocery store or dollar store for my dog.. if you had a larger breed dog you might be able to get away with it, but yorkies are so small and they eat so little that it's important that the food they do eat be of higher quality. you just have to experiment and find what food is right for him, every dog is different. a lot of higher end brands will offer samples of their product, i think there's a thread for that around here somewhere as a matter of fact. miles is eating blue buffalo life protection for small breed dogs and he's doing really well on it.. his digestive systems stays very regular, which helps with potty training, another plus
