This is NOT my solution, this is a cut/paste from BiggDope's solution from 2015. The guide is for the non GOTY edition of the game but should still be the same. The achievement is available in the Hearts of Stone Expansion. Comments in the original solution have noted that simply owning the armor would not be enough to unlock the achevement (unconfirmed). You have to be level 38 according to the Gamespreassure Game Guide to wear the armor.
Link to original solution:
You can begin making progress on this achievement by speaking with the Ofieri Merchant located at the Upper Mill fast travel point in eastern Novigrad. Ask to take a peek at the man’s wares, and proceed to purchase the following items:
+ Decorated Saber - ~2500 crowns
+ Ofieri Blinders - 233 crowns
+ Ofieri Saddlebags - 233 crowns
Back out of his inventory menu and comment on his horse. This will spark conversation and lead to the opportunity of racing the Merchant. Do so, and if you win you will receive an Ofieri Saddle. Now speak with the Merchant again and exhaust all of the dialogue options until Geralt mentions that he can recover the Merchant’s lost diagram pages. This will initiate the “From Ofier’s Distant Shores” quest. Tackle this quest however you’d like (take note that three of the four diagrams are located at campsites that you will be looting for the Wild Rose Dethorned achievement) and once you have collected all four diagrams, return to the Merchant, meditate for 24 hours, and then collect your reward: translated diagrams for Ofieri Boots, Gauntles, a Tunic, and Trousers.
Now you will need to collect the necessary crafting materials before heading out to the Armorer in Crow's Perch to craft your four-piece gear set. Once it’s crafted, the achievement should unlock provided you have all 8 pieces of Ofieri Gear in the game.