The best food for your dog is the one you can afford and with which your dog thrives.
There is nothing in general about canis familiaris that excludes feeding starch (cooked grains); there is genetic evidence that dogs developed (about the time of domestication) the means to digest starch. However, this information is about population genetics and not about individual genetics; an individual may not be able to tolerate certain foods. So the diet for an individual may need to be tailored in order for that individual to thrive.