You can win rewards by playing and ranking high on the leaderboards.
Weekly Rewards
Each season of the game has 4 weeks, and a set of rewards are given every week, based on the players' ranks at the end of the week; the weeks start and end every Monday, at 2 pm UTC.
Leaderboard
There is a separate leaderboard for Constructed and Discovery game mode. The two game modes each have a set of top 500 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!
Each leaderboard is a consolidated list of the top 500 players regardless of rank (from Apprentice to Grandweaver) prioritizing rank, and then ELO within each rank.
You can find more about the 7 different ranks here.
Rewards
Silver cards and Conquest tickets are awarded to the weekly top players on each leaderboard. The rewards are as follows:
Top 1 - 10 Silver cards and 2 Conquest tickets
Top 2 - 9 Silver cards and 2 Conquest tickets
Top 3 and 4 - 8 Silver cards and 2 Conquest tickets
Top 5 and 6 - 7 Silver cards and 2 Conquest tickets
Top 7 to 9 - 6 Silver cards and 2 Conquest tickets
Top 10 to 13 - 5 Silver cards and 2 Conquest tickets
Top 14 to 19 - 4 Silver cards and 2 Conquest tickets
Top 20 to 31 - 3 Silver cards and 2 Conquest tickets
Top 32 to 65 - 2 Silver cards and 2 Conquest tickets
Top 66 to 100 - 1 Silver cards and 2 Conquest tickets
Top 101 to 250 - 1 Conquest ticket
This list will be updated as needed.