Through the pioneering efforts of the golf pros such as Ben Hogan and others, it is certainly OK to wear a hat while playing golf. And Walter Hagan brought the Aussie-style straw hat into prominence, so there are a variety of hat choices you can make. Beside golfing and baseball, where can a man wear a hat in a casual setting? The golf hat is both stylish and serves some very useful functions, such as keeping the sun out of your eyes when you are making that critical shot, and more importantly reducing the chance of the negative effects of excessive sunlight exposure (skin cancers, heat stroke, serious dehydration, etc.) Sunglasses too, are superb and required accessories. The most popular sunglasses are the sun blocker types that reduce UV radiation and give a clearer view of the golf course even under harsh glaring sunlight conditions.
Moving on to the golf shirt, this is where the best choice is a understated robust short-sleeved t-shirt or cotton knitted tee, that displays a small logo of a frog, alligator, sports brand logos like Nike and Puma, or designer brands like Ralph Lauren's polo logo, Tommy Hilfiger or something similar. These type of shirts have little significant design differences except for the tiny logo difference, as to almost represent a kind of uniform. Almost every label has one of these type of shirts so just select the one you like, that feels the most comfortable. Don't be afraid to pick the one that is hot pink or bright yellow, as this can always be played off as an attempt to distract your opponent to gain the competitive edge. If you do go with a very vibrant color of shirt, make sure you don't cross the line with also excessive patterns on the shirt. Unless you are actually in Hawaii, do go for Hawaiian flower shirts and certainly avoid tank tops.