"gold is a bit trickier because the DC of gold increases if an NPC is carrying more of it."
All you have to do is right-click on the gold stack and select "split." Splitting it into smaller stacks makes the new stacks easier to steal.
Steal their gold, buy the items you want, then steal the gold back. If an item is still to pricy after you stole their gold, then take a long rest. That recharges their gold on hand. Steal that new gold, buy the item, then steal the gold back again.
I don't even feel guilty because my rogue is a thief after all. I'm just staying in character!
