To start, go speak with Lazare Lafargue and he'll give you the secondary quest Master Master Master Master! which then gives you access to the 5 grandmaster gear quests, though you only need to complete 1 for this achievement's purposes.
Once you have a set, have him craft all the pieces and equip them to get the achievement to unlock.
As some of the grandmaster armor requires previous versions, if you don't have these focus on either the Grandmaster Manticore or Wolf sets.
If you're just aiming for the achievement and time is a concern, focus on the Wolf gear. All the diagrams are in one location.