You can win rewards by playing and ranking high on the leaderboards.
Each season of the game has 28 days, and a set of rewards are given every week to the top players; the weeks start and end every Monday, at 2 pm UTC.
There is a separate leaderboard for Constructed and Discovery game mode. The two game modes each have a set of top 250 players and rewards to be given. You can focus on one or try both to increase your rewards. The higher you rank, the bigger your rewards!
You can find more about the Ranking system here.
Silver cards and Conquest tickets are awarded to the weekly top players on each leaderboard. The top 100 players will receive silver card/s and Conquest ticket/s. The top 101 to 250 players will receive only Conquest tickets.