I'm doing a second playthrough to see if I can get a different ending. I really enjoyed this game the first time around. But enough of that.

On this playthrough I can't seem to start a Gwent game. At the very first game when I hit start I got the message "not enough unit cards" and didn't pay it any mind. I've since bought cards from a couple of merchants and tried to play again but every time I try to play I get the same message.

What "unit cards" am I missing? They seemed to have been there automatically in the first play through.

You need 22 unit or hero cards to play anyone other than "tutorial guy", plus "upto" 10 modifiers. When you beat him he gives you one more card.

I think you are strictly limited to Northern Realms at the beginning and should buy all the cards from Elsa to bukl up your deck. As far as I know, the next potential opponent is the Nilfgaardian Nobleman (I don't recall there being anyone else in White Orchard).

Before you play, you need to press H & shift what ever Northern Kingdom unit cards you have in your collection over to your playing deck.
Until you have 22 unit cards.

Thank you very much. That's what I needed. The first time through I used the tutorial and it told me what to do.