Medium blue solid is liked by almost everyone and can be worn by most men. Medium gray solid is good for dealing with professional but should not be worn by heavy men. The best suit to buy for interviewing is a vested dark blue solid. By changing shirt colors and ties, different looks can be achieved, and each will be professional. In this climate, wool is usually too warm, but generally, the higher the wool content, the richer looking the suit.
Textured polyester is all right if it looks like wool.
Polyester also has the advantage of not wrinkling too badly when worn in hot weather. Some cotton or linen suits are fair but they wrinkle very badly after only hours of wear. It is best to avoid nylon, rayon, mohair, silk, denim and corduroy. Never be afraid to ask that something be altered. You are paying your good money, and the store owes you a proper fit.