You can feed him/her Eukanuba or Royal canine. Both are good dog food. They may be little expensive but if you buy it in bulk it may be a little cheaper. The best thing will be to first try a trial pack. If the dog looks fine eating the new meal, you can go for a bigger pack.
You can also feed variety of home-cooked diet like chicken-chest, rice, yogurt, bread, paneer. They are fresh and preservative-free. Dogs like variety.
I personally, feed home-cooked food to my dog.