There are
four three Witcher gear sets, you need to complete one to get this Achievement. The Treasure hunt Quest can be started from picking up Notes, they can be looted from a Body or bought in a Shop (like in the Screenshot below), but you don’t need any Maps for Info you can start also the Quest if you pick up any part of the Gear. There is not first and last Item, you can get them in any Order. You need to build and equip the Gear to get the Achievement
Scavenger Hunt: Griffin School Gear (Six Items)The second Set are six Items and both can be found in Velen.
Dragonslayer’s Grotto #26 at the Map (SE): Witcher Gear: Diagram: Griffin Armor, Griffin Trousers, Griffin Boots, Griffin Gauntlets
Hindhold #27 - NE: Witcher Gear: Diagram: Griffin Steel
Lornruk #1 - North: Witcher Gear: Diagram: Griffin Silver Sword
Here is a List with almost every Gear and Upgrade Location:
https://wiiare.in/portfolio-type/the-witcher-3-wild-hunt-arm...