Where do I get Battle Coupons?

Battle Coupons are used to receive rewards at the end of a Ranked match.

There are two ways to receive Coupons:

1. You get 20 Coupons for every League-up (these Coupons can exceed the limit, for example, you can have 40/20 Coupons).
2. You get 1 Coupon every 30 minutes when you have less than 20 Coupons left.