Ok what can you afford? I'm not trying to make you feel bad as I am a full time primary carer for my mum and potless most of the time.
Feeding stuff like Wagg, Eukanuba, Bakers, anything by Purina, Beta Puppy being one, is like feeding a child on sausages, beefbrgers, sweets and cakes which are full of sugar, additives and fillers. Don't just be swayed by price either. Stuff like Royal Canine is not entirely natural and unless we all did life long studies of which dogs were better on which foods, we will never be entirely sure.
As a responsible pet owner, you should try to feed you dog the best diet you can, remember your dog relies entirely on you to make the choice. By attempting to give a good healthy balanced diet you are helping your dog remain healthy and ultimately this will result in smaller vets bills.
Nutrition for a small puppy is vital, just like for a growing child. Unless you are an experienced BARF or raw feeder and I am not, I would suggest a good kibble like Burns or JWB, or Healthy Paws. You can supplement one meal twice a week with one raw chicken wing or a some tinned sardines or pilchards. You can also give your dog raw veg finely chopped and fruit. This means the kibble goes further. The kibble and raw bones are excellent for teeth.
You should not feel compelled to purchased very expensive stuff like Royal Canin which isn't necessarily the best anyhow.
Go for the purest and healthiest kibble you can. Afterall what you feed a puppy is the very foundations of the dog you get in the future. You want, in theory a healthy dog, then pumping them full of colourants, sugars, cheap fillers and additives is more than likely going to give you costly and unpleasent illnesses in the future.
I hope that helps.
