After playing a second time doing the new game plus (with expansions), my main goal is to not have "Failed Quests" or any failure inside the normal quests. Going to the masqarade ball to save Albert, started to play the Gwent game there but kept getting beat by the guy playing the Monster Deck. I'd be in the 20's and he would be well over 100.
This is the one quest I find that is impossible to beat because of some of the Gwent games are inside of the different quest and does not give you a chance to get better cards and come back and play again.

stu

It's Gwent.

Just hold on doing this quest (it will be available as long as Triss still in Novigrad) until you assemble a better deck.

I normally don't put weather cards in my playing deck, but the easiest way to beat monster deck is to use biting frost. It's ridiculous how one biting frost can annihilate even the strongest monster attack; reason being almost all of the monster deck's strongest cards are melee. With a well placed biting frost, even a commander's horn on the melee becomes useless.

Before playing against the last guy, put 3-4 biting frost cards in your playing deck, and use little to no melee cards yourself (doesn't apply to heroes) so that you can avoid your own biting frost.