**3/9/21 Update** ~ Requirement went from level 25 to 45 in the Gold Hoarders Faction.
This achievement is, for the most part, very straightforward. You do the 'new' Treasure Vault voyages 3 times.
However, there are 2 different types and only 1 of them provides Gold Vault Keys which are what you desire. These are obtained from the Vault Voyages given by the Gold Hoarder guy in the tent. Larinna, the newer NPC standing outside the tavern, gives the same type of voyage, but it ends up with Stone Vault Keys (iirc).
The Gold Hoarder variant also gives better loot and cooler vaults as I've seen so far.
**** Note: You must be level 45 in the Gold Hoarders Faction to be able to buy the correct voyages.