Medieval Fantasy: Dark Witch Concept

Trying to stick to a criteria I am not used to exploring, I am creating a dark witch in a fantasy medieval setting.
Having played Dragon Age: Inquistion, I decieded to base this character of the aesthetic of Vivienne/ Madam De Fer. Although given the theme, it is proving quite difficult concepting clothes that isn't a dress, aiming to keep it regal and elegant, yet practical.