What do you feed your dog and why?

I am looking into new ways to incorporate some new foods into both my dog's diets.
It's something I'm starting to think more and more about.

I currently feed them on Arden Grange kibble. Arden Grange seems like a good quality, ethical food to give them. Please correct me if I'm wrong, but that's what I hope is true.

I don't have enough time on my hands to give them a homemade raw diet. But I'd like to add some more variety to their meals.

I often add fresh chicken to their kibble and also bits of left over veg, pasta etc.
One of my dogs, Kimmie, really loves having gravy on her food. She can't get enough of it.
She likes having Pedigree tinned meat in gravy too.
I'm trying to find a gravy that I can buy to mix up with the dog food. I want one without added salt, MSG etc.
I don't make gravy from scratch myself so I really need to find a good powder or a tub of gravy I can buy.
Does anyone know of a good one for dogs, maybe even an actual specific gravy meant to be fed to dogs?

I've also heard of people adding cod liver oil to their dogs food which supposedly gives them a good shiney coat and is good for their joints.