What are some easy ways to get brawler shards in Super Brawl Universe?

The Nickelodeon game, Super Brawl Universe, has brawlers that you can be obtained by tournament rewards, campaign, or purchase.

All of these 3 things to get brawler shards are very rare, so I am asking the easiest way to get them.

I tried Auto-winning battles, as a game tip suggested, but 25% of the time I get a brawler shard (0 – 1). For tournaments, you can get 2 – 6 brawler shards, but it takes days for the event itself to finish and it requires grinding to get x2.

What is the fastest and easiest way to get some brawler shards overall?