It depends on what you are looking for and your dog? Does it have an easily upset stomach? Are you looking for a dried food you can soak in a bit of water to release the flavour? Something for allergies?
I like James Wellbeloved dried feed. Its lamb and rice or turkey and rice kibble and is best when soaked in a bit of warm water before feeding. Its not cheap though, about double the price you pay for most brands. I think a 20kg sack is £30 plus. But some dogs don't cope well on it. Others do.
For my older dog I use Chudleys senior. £14 a sack and he does fine on it. It suits his needs and I never vary it.
Chudleys also do a wide range of feed for working dogs, young, old, etc.
I'd suggest going to your local feed merchant (not pet shop) and seeing what they have and reading the bags as to whats in them etc.