60 non-legendary set isn’t good enough to justify replacing your 55 pvp set unless you strictly do just pve. It will be awhile before anyone can get the full 60 legendary. The optimal way to get the stones is by using stockpiles of keys on the summoner which the level 60 dungeon doesn’t have.
So you’d have to do the level 65 dungeon nightmare. Here’s some of the mats for one piece of gear.
150x stones which can count for roughly 200+ skeleton keys
15x armor/weapon shards which is 12000 insignias
You can make the pieces if you want, no harm in that but don’t expect it to be turned into legendary for a long time.