Playing Season Challenges gives you more rewards the more you play. Purchase the Gold Pass to unlock even more, Gold Pass exclusive rewards.
Without purchasing the Gold Pass, you only get the rewards in the bottom part of the Rewards track:
With the Gold Pass, you get all the Silver rewards, but also Perks, more capacity to the Season Bank and a Hero Skin:
Remember to collect your rewards before the season ends. Only unlocked Hero Skins are collected automatically for Gold Pass holders at the end of the season!