Some of these change how the round goes. Most do not. Here is the difference.
Accessories are where golf spending goes quietly out of control, because each item is small. A short list actually earns its place.
A golf glove should be tight enough that there is no loose material across the palm, with no spare length at the fingertips. A glove that has stretched out is worse than no glove — it slips. Leather gives the best feel and dies fastest in wet weather; synthetics last longer and grip more consistently when damp. Most players wear one on the lead hand only.
Four hours of direct sun on your face and scalp. A visor keeps the head cooler; a full cap protects the crown, which matters if your hair parts. Either beats neither by a wide margin.
Thicker than everyday socks, and the reason your golf shoes should be fitted in them. Cushioning at the heel and ball, and a fabric that moves moisture — blisters on a walking course come from damp cotton more than from friction alone.
For club faces and grips, not decoration. A wet grip is how a club leaves your hands. Clip it to the bag where you can reach it without stopping.
Sunscreen, reapplied at the turn. Nothing else on this list matters as much and nothing else is forgotten as reliably.