The foundation of a healthy cat diet is a meat-based protein like fish or poultry. Dry food should be high in animal proteins, and low in plant proteins (which cats are ill-equipped to digest). Carbohydrates should make up no more than ten percent of the cat food ingredients.
Wet food is preferred over dry as the meat is more plentiful and moisture is added. Neutered male cats must be fed wet food as they tend to drink less. Less liquid intake means their urine is more concentrated and the likelihood of urinary tract issues are increased.
The best wet food you can buy without a prescription is, believe it or not, Fancy Feast. Pretty any much any variety is 87% digestible protein. The highest of any OTC wet canned food.