Best Method of Gold Acquisition?

[The Legendary Joe]

Okay, with multiple quests coming down to needing lots and lots of gold, I have to wonder what the best ways of actually getting Golds is.

I thought mining would have been good, but it seems I only really get gold from the minigame anymore.

Gift boxes seem like a decent source, but they're pretty random.

And I've been told Blank cards are decent at getting gold too.

Most mobs that drop it, it feels I might as well be card hunting. Is there a specific type people hunt for it?