Try the 'litter tray' forum on here for some good threads about cat food
Personally, we use Royal Canin dry food for ours with a bit of Waitrose wet food per day. Sounds expensive but she eats much less than the cheap stuff (Felix and whiskas) that she was eating when she came to us!
I used to feed my friends four cats when she went away. I often to go in to find runny cat shit all over the house. I d been left tinned food and dried food. After a few days I twigged the dirty days came after feeding them the dried stuff, and stopped feeding them it. No more pooey carpets. My friend loved me for making the connection, apparently they'd been doing this for ages, but not told me. Thanks mate! I think the offending item was Go Cat, and it certainly made them do that. I think it had a high wheat content which cats dont need. That is the end of my wisdom on cats food, but thought it worth sharing!
We have a 14 week old kitten. He's on Asda Tiger Kitten pouches and Whiskas Kitten dry food. Fit, healthy, incredibly active, gaining proper amount of weight, shiny coat. He was being fed on that when we got him at 8 weeks and he seems to be thriving on it.
cheapest healthiest and easiest way iv found is buying those packs of cheap meat from the butchers. the liver and kidneys for 99p etc and whole fish from the supermarket . preparing these foods raw can be tricky and messy so i just whack them in the oven and portion it out between the cat and the dog at dinner time. my cat is an excellent hunter so tends to feed himself during the day then home for supper and a nap lucky cat. i find if i cook chicken for the family some of that will keep the cat happy for a couple of portions. i view any pre packaged pet food as a ready meal. you take him off his fast food diet and swap to whatever works for you both be it raw or cooked homemade food and his skin will clear up and his eyes will shine he will thank you for the effort!