Puppies up to 1 year old need good quality specialist food for development.
After that I would check the ingredients on the dog food nuts - many of the cheaper brands are just bulked out with meal and lacking in many nutrients - leading to dogs getting bored of them very quickly. At the same time, most of the "better" foods are very expensive.
Most dogs love bones - ask your butcher for raw marrow or lamb bones (not pork or chicken). These can be frozen if necessary. As the butchers are charged per weight for bone disposal, they are more than happy to give them away.
Other options include buying cheap cuts of meat/mince/liver etc and making your own dog food casseroles with carrots, peas, pasta, rice. Include potato skins and any other leftovers that are suitable. Dice the meat up small and it will go a long way. Include some oil for their coats. Again these can be frozen until required.
If your dog will eat fruit (as mine do) give bananas and whole apples as a treat - cheaper than the treats you buy in supermarkets. Raw eggs also a great treat.
May not work out much cheaper in the long run, but you're guaranteed a happier, healthier dog.