Update: As of 5.3 this is obsolete. You can only buy Augmented gear now. See this post for the latest info.
I made this post so that I could easily upgrade my Ironworks and Shire Gear. There are a few places to find the info, but they are not convenient to refer to. This is designed to be easy to use.
Note: Next time I visit Rhalgr’s Reach, I’ll add the guide to upgrade the level 70 Scaevan gear. The purchase and upgrade NPCs are all at the same counter for the Scaevan Gear.
Upgrade Ironworks – Level 50 Gear
Purchase of Ironworks gear is in Revenant’s Toll, Mor Dhona. Purchase the gear from Auriana at the counter on the upper level. Auriana also has Upgrade Mats under the Other category of her store.
Purchase a single Carbontwine for Armor and Weapons, and a single Carboncoat for Accessories.