Play a friend, set up a deck that allows you to draw cards and/or cheat Marin into your hand. That’s what I did, I completed 13/15 of the quest requirements in less time than it took to complete the first 2/15 playing ranked wild.
NOTE: (1)The previous 75 pirates quest requires play in ranked mode, but Marin’s quest does not.
(2) Do not overfill your deck with draw cards, as you can fill your hand with cards that just draw more, preventing you from getting Marin’s treasure cards that you need.
(3) Zola the Gorgon was useful for duplicating Marin.
(4) I used rogue. The 0 cost “return a minion to your hand” was very useful. Cleric may work as well, as that class has a few “discover a minion from your deck” or “discover a spell from your deck.”