That really depends on you. If I had to face that choice, I would upgrade my golem to the max, since they receive huge boost for each level, and they're the most critical part of a successful Tank/Damage combo in higher league (GoWiWi/GoWiPe/GoArch/GoWiz)
But if your golems are at lv4, and you can wait, then I see no harm in upgrading your wizard.

