Prince Uniform

The Princess is the vendor, and she is the hardest one in the game to unlock. She only moves in once every other town NPC is alive and housed in the same world at the same time, which means a Hardmode world with every rescue done and nobody left dead in a corner of the map. Until that roster is complete she does not appear at all. The outfit is effectively a trophy for a finished town rather than something you pick up on the way through.

Three pieces, and none of them is headwear, so the head slot stays free for a crown, a helmet, or just your own hair. The cape does most of the visual work, since it trails behind you and stays readable while you are moving, which is more than most vanity can claim in a fight. All of it goes in the social slots, so a full royal look costs you no defense. It is the counterpart to the dress the Princess wears herself, so two players can dress as the pair.