Once a man has the minimum ten or twelve dress shirts that he needs, his wardrobe benefits from a little thought about how his collection should grow. His basic wardrobe of course has a couple of white, a couple of pacific blue on white candy stripes, perhaps four blue solids, a gray and/or an ecru solid depending on his coloring and a burgundy candy stripe (candy stripes are suggested as they can be worn successfully with pin striped jackets).
Past that dozen, which should be in medium-weight cloth such as end on end, the wardrobe should grow to encompass heavier and lighter weights for better temperature control, and more patterns to enable a wider variety of looks. That means broadcloth and nailheads for cool weather and voiles and high twist weaves for summer. For the patterns, add a couple other stripes and some checks to the mix.
The most wardrobe flexibility is achieved with semi-solids and simpler patterns in a palette that has blues from pale through periwinkle to navy, blues on white grounds, grays on white grounds (solid gray is difficult with many complexions), tan, and tan on white grounds. Choosing a shirt, jacket and necktie from each color and limiting the combination to no more than two patterns produces consistently excellent looks with a minimum of fuss while spreading wear across the entire rotation.
There is no upper limit to the shirt wardrobe of course, but cotton ideally requires several days of rest after each wearing and one shirt for each day of the month is a reasonable middle ground.