I would absolutely avoid the cheapest food, of course (store-brand food for example).

What lifestyle does your cat have? Is it indoors all the time, or outdoors all the time, or some of each? Outdoor cats will supplement their diets with all kinds of things that they can catch, so a lower quality dry food might be OK for them. I've just moved and switched Sasha to Science Diet Hairball Control, since she won't be going outside anymore (we've moved to an in-town location, from a rural neighborhood) and I wanted her to have a little higher quality food because of that.

Also, I have heard that feeding primarily dry food is better for the health of teeth and gums, and wet food should be more like a treat. Maybe someone with a little more experience here could tell me if that's true or not.