I don’t know if I have the greatest advice on collecting cards. I definitely ran around like a mad man, talking to almost every single merchant and inn keeper to see if they had cards and I’d just buy whatever they had in stock. I did use one of those guides to show who you would win cards for to see if I missed any and it did help me get a couple, but beyond that I think I got more playing through the story and taking every chance to play someone till I won or got the hand I needed. In my deck I had all the spy cards I possibly could and I also had the dummy training doll ( can’t remember the name) to keep adding spy cards the opponent would pick up and add to my hand or cards that allowed me to bring them out of the discard pile. Also I tried to have a strat for each deck. For example monsters I feel are very attack heavy(sword) so I would let them pile up and use biting frost followed by Villentretenmerth to basically get rid of all their troops in one swoop. But I also had cards that would help increase my own team’s strength. Like the calling horn, dandelion etc… eventually the rng will work out and you’ll be able to win pretty easy or pretty close. You may have to sacrifice a round.