There are several ways to get new cards:
•        Free packs:
You get one pack of cards for free every four hours, which you can claim your Free Pack from Cartman's Shop. Cartman can store up to two Free Packs at a time. After two unclaimed Free Packs are in his shop, you won't be getting the next one. Keep checking back and claim those Free Packs.
•        PvP packs:
You get PVP Packs for victories in PVP Multiplayer. Need more cards or coins? Jump into PVP, win some battles and earn yourself a pack!
•        Loot lockers:
Each time you beat a Campaign stage or defeat an opponent in PVP Multiplayer, you get to open three of the ten Loot Lockers. Somewhere inside these lockers are super sweet Special Rewards!
•        Cartman's shop:
Buy some cards for coins in Cartman's shop. Remember that stock is limited, but Cartman always manages to get it replenished each 24 hours.
•        Butters' shop:
Butters also has his own shop, except, being a Don King Butters, he sells his merchandize for PVP Tickets. Just like Cartman, he replenishes his stock each 24 hours.
•        Premium packs:
Last but not least, you can choose to buy yourself one the Premium Card packs for Cold Hard Cash.