In the Blood & Wine expansion, you have the option of upgrading your mastercraft witcher gear sets to an additional tier – Grandmaster. This gear is not only higher quality and level (40), but also provides you with two unique set bonuses.
The process of obtaining it is the same as previous sets – you will first need to find the diagrams, and then craft the gear at the smith.
To find the diagrams, talk to the Grandmaster Smith in southern Beauclair – he will start the Scavenger Hunt quests for finding the Grandmaster versions of Wolf, Griffin, Cat, and Bear school gear.
A word of caution, however: grandmaster gear is very expensive, especially if you don’t want to gather all the required materials yourself and would rather buy them from merchants. If you don’t have the cash, one lazy workaround is to install the Witcher debug console and use the addmoney (#) command.