From what we can see so far, Coriakin's outfit consist of two layers: a long-sleeved gown and an open robe.
The floor-length gown looks like a brown or possibly moss-green color. It has a standing collar and wide flared sleeves gathered into the armscyes—see this image. Looks like it might have a sash or a belt.
The sleeveless, floor-length open robe is a goldish moss green with reds and browns, possibly a brocade. It also has a standing collar. The armhole and open front are edged with piping. In this image we see that the lower half of the robe has a slender dark line that widens into a diamond design, and then into a panel that extends to the floor—is this woven into the fabric? Inset? Applique? Better pictures will tell.