Once you've opened a Vault of the Ancients, you have approximately 3-4 minutes to get in and either grab chests, grab the tokens to open the door to the Ancient chest and/or grab money!
For this achievement, simply press X (on Xbox) to hoard all the piles of gold. This takes around 3 to 5 seconds per pile.
Be wary though, there are also a lot of piles on top of wooden structures! Some platforming is needed. I got the achievement while underwater inside the Vault, died after getting the achievement because the "Vault-timer" was done and I drowned. I was just in time. Best be done with 2, 3 or 4 players, but doable with just 2.