Either T6 Rift or T6 Bounties
Using:
Boon of the hoarder
Custerian Wristguard (gold = xp)
If it dies a lot use GoldWrap belt
Optional:
illusory boots
Unity
Option 1
WD Pet Build
Thing of the Deep Mojo (+20 pickup range)
Option 2
DH M6 Build (ferret will pick up gold)
I choose this 2 because of the gold pick options you have, but you can try other classes as well.