tbh, unless your cat has specific needs your standard meow mix, friskies, fancy feast, whiskas and shit will do just fine. When they have more specific needs then you look into specialty premium foods. natural choice has a lot of good options, science diet has more of those hairball/UTI/sensitive stomach/sensitive skin formulas though. Blue buffalo, avoderm, royal canin and stuff like that are higher end with whole ingredients though. Like none of this processed crap gets in those. #1 ingredients will be the meats, whereas in science diet you'll get stuff like meat by-products and corn and shit as the first couple ingredients.

I'd go into a petsmart in the area that has a banfield and ask one of the people there to show you something for your specific needs. They know a hell of a lot more than your regular jagoff associates do by far. Though they might want to put em on a prescription diet, which will cost more than what you are paying for food now. But ask em. It won't hurt.