Villa-Swashbuckler. When you have Treasure Chest (from Swashbuckler), you gain a Gold every time you enter your buy phase, including from Villa. This allows you to gain a lot of Golds very quickly. However, you need to be careful not to gain so many Gold such that you can no longer draw your deck.
If you draw your deck and have $4 and additional draw in hand (such as a few cards that give +1 Card, +1 Action), you can gain as many Golds as you have draw cards: go to your Buy phase and gain a Gold, buy a Villa, go back to the Action phase, draw the Gold you gained, go to buy Phase and gain another Gold, use the previous Gold to help buy the next Villa, etc.
Villa also provides a way to get Coffers from Swashbuckler even starting from a clean shuffle: play a Villa for the +Buy; buy a non-Villa card, then buy a Villa, returning to your action phase so you can play Swashbucklers for the Coffers.