Well I would use one Gem of Ease in the socket of a 2h ancient weapon (Wormwood seems decent) and the second one to remove the level requirement on Custerian Wristguards (XP for Gold drop). Furthermore, using Hellfire amulet and ring (they both have no level req.) with the highest dmg rolls, and at least one socket to use with a Boon of the Hoarder (ideally lv 50) should help as well getting you asap to Level 70. I guess running vaults from Puzzle Rings or HoA3/Ruins of Corvus, should be the fastest.
For the cube, maybe a Maximus might be good and even fun to use