Bring 8 Pristine Spider Silk to Wynne Larson in Stormwind.
Your service has been unwavering, [player]. I think, perhaps, it is time you had a finer garment, one more suiting your station as an adept mage. If you gather the needed materials, then we will arrange the robe made.
You must enter Duskwood and hunt carrion recluse spiders. Extract their silk, but only the finest, most pristine silk will do. When you have enough, take it to Wynne Larson, here in the mage district at the Larson Clothiers. She will craft your robe.