Do some research on dogs and wheat intolerance, and then look at how much wheat is used to bulk out most dry dog foods.
I think most people would be surprised at how bad most popular dry dog food is. Take a look at this website http://www.dogfoodanalysis.com/dog_food_reviews/index.php if you want a bit more info before deciding on what food.
I feed my springer on Skinners Field and Trial Hypoallergenic after realising how unhealthy foods like Bakers, Wagg, Pedegree, Eukanuba, Iams etc were.
You’ll find with a cheaper food that you will need to feed them more in order for them to get the nutrition, so it’s sort of false economy. A £25 VAT free sack of Skinners lasts my Springer about 6 weeks.
That probably doesnt help you at all with your original questions about puppy stuff but that’s just my thoughts on dog food.