By Danbooru's definition of the gothic tag, Miku isnt wearing anything gothic (which I disagree since goth styles come in various forms, from the outrageous spiky all-black clothing, to the cute loligoths of Japan... IMO, this is just a form of casual goth; not too extreme).
Im gonna add the tags punk, which suits this pic better (by Danbooru standards), as well as punkish_gothic which also might fit, as well as being both gothic AND punk, lol.