Sephiroth armor???
Have you tried going to your bank, clicking on Wardrobe, and then just trying on/previewing all of the skins for light armor? That’d probably be the best way for you to find the exact look you’re going for.
You can do a google search for it and see if anyone has come close. Just look at the images only when you do to make it easier. There are a lot of people who cosplay characters from other games with their GW2 characters so you may find something close to what you’re looking for.