In the first season she was the only member of the main cast who wore the minidress variant of the uniform. Like they tried to bring forward the gogo dresses that Uhura, Rand and Chapel wore in TOS, and in an attempt by a Silent Generation geezer to be progressive and/or justify Marina Sirtis having her legs out, they had a few male extras wear the minidress uniform in the background as well.

Second to ~5th season she wore a collection of spandex jumpsuits, ranging from lilac to maroon but I also remember a green one that had kind of a flowy skirt to it. Then they used the whole THERE ARE FOUR LIGHTS episode as an excuse to have her wear a uniform. Sirtis was pushing for Troi to wear a standard Starfleet uniform, and having Captain Jellico awkwardly order her to was how they solved the problem in-universe.

I personally would have either written her as a civilian contractor, putting her in the same community as Keiko, Guinan or Mott, OR I would have put her in a uniform with a coat like Dr. Crusher since Troi was the ship's psychologist, we don't really see this but she should report to Crusher the way Barkley reports to LaForge.