For cats, the corn, grain, and otherwise carb-filled cat foods that dominate store shelves and are cheaply available are absolutely terrible. Cats are obligate carnivores and aren't built to deal with that kind of food composition at all. Some cats deal with it better than others, but generally feeding your cat these cheap foods will result in it becoming very obese and highly prone to several types of disease.

I don't go as far as some pet owners, buying frozen pet food from Whole Foods and the like, but I do buy my cat high quality meat-based grain-free dry cat food. It's a little pricey but a 9lb cat eating proper amounts of protein doesn't eat much and a large bag lasts a long time. Just make sure to get a good airtight container to keep the food in.