Very easy to get. Just play as the Rogue, and play against the Alchemist as a "Local Player". The Alchemist starts with 5 gold, the minimum amount needed for this achievement, and can turn Objects into Gold at any time if needed. Just land the Rogue on the Alchemist's space, Encounter the Character and fight them, win(reroll for both to get the best result if needed), and choose to take their gold. Achievement unlocked!