If it's a transit, it's a good time to focus on spiritual advancement, and if you are the creative/artistic type, to include that side of you more into your outer life. The 1st house is outward projection.
If you mean in a natal house, this placement can give artistic/musical ability, a closeness to spirituality, a desire to know the Gods. This placement can give one an ethereal beauty to their appearance.
Don't let drugs or alcohol sneak up on you, there have been people who associated with others, tried something, and then became an addict. Neptune doesn't have boundaries, so anyone with a strong Neptune needs to develop the trait of having strong boundaries. I know this isn't what you asked, but I wrote it anyway for anyone else reading this.