So like Gwent and stuff. I just figured out how to play it and made it my mission to travel the country and play every possible npc. I had to fail a bunch on the soothsayer in Velen in order to figure out how to win and I went from vendor to vendor to pick up cards when they sold them. All after I missed a rare one from Velen, the Bloody Baron (that quest was great btw, don’t regret anything just make your choice and move on), I resolved to get good play everyone I could. I missed some of the rare ones from White Orchard as well but it doesn’t seem to be handicapping me at all. I just won’t be able to “catch them all.”
I doubt I’ll ever get into the actual card games like Magic: The Gathering or Hearthstone but I’m definitely liking it as a side game in the Witcher 3. Its the most fun I’ve had playing a mini game in a rpg since the various mini games in Final Fantasy 7.