The Witcher 3 gwent all cards (Gwent / gwent) are organized by region: each table row shows strength, faction, the exact place, and whether you buy the card or have to win it.
In White Orchard you start with the scholar and your first purchase. Then come Velen, Novigrad with Oxenfurt, Skellige, and in the Blood and Wine expansion Toussaint with the Skellige deck. You get the book A Miraculous Guide to Gwent by beating scholar Aldert Geert at the inn in White Orchard. It shows how many cards you still miss in the region.
How you get cards
You pick up cards three main ways. Buying from innkeepers and merchants. Winning in quests like Gwent: Velen Players, Gwent: Big City Players, Gwent: Old Pals, High Stakes, Gwent: Playing Innkeeps, and Gwent: Skellige Style. Random wins from ordinary merchants and blacksmiths. From each such player you get one card from the shared pool on your first win. When the pool in the region is empty, you only get crowns and junk.
Special cards (decoy, Commander’s Horn, scorch) have no unit strength. The table shows a dash for strength.
By region
Pick the region you are playing in. On the card you find an interactive map with pins for players and merchants and a full card table.
Random wins
The rest of the collection (Nilfgaardian spies, more Scoia’tael, weather, Villentretenmerth, Emiel Regis, and more) does not hang on a specific quest. You get them from ordinary players with no journal name: merchants, blacksmiths, armorers, and sometimes innkeepers outside the tables above.
The mechanic is simple and always the same. On your first win against such a player the game gives you one card you do not have yet. It does not pick based on who sits across from you. It draws from the shared pool of cards still left. At a blacksmith in Zalipie you might get a completely different card than at a merchant in Crow’s Perch, and after a reload the next try can drop something else again.
You play for a card with the same person only once. Another round with them no longer gives a card, only the stake and junk. You know it when you win and no new card appears.
There are more players in the region than cards in the pool. When the pool runs out, card wins stop even from new opponents. Then it is time for the next region, remaining purchases, or quest uniques. A Miraculous Guide to Gwent shows how many copies you still miss in the area. It will not tell you who holds which card, because random wins do not work that way.
Conclusion
In each region buy every card from innkeepers and merchants first, then win the quest matches, and finally visit ordinary players. Watch the book A Miraculous Guide to Gwent as you go. When the regional number matches and something is still missing, you almost always missed a one-off quest or Olivier before Now or Never.
You get Foltest’s card in Vizima and the secret room in the palace garden in the Vizima guide. The big picture on the game is in The Witcher 3 review. More guides sit on The Witcher 3 hub.