Play games
Choose the game that interests you and play itfor free.
Complete the quests
Every game has some quests for which you will receive Soul Gems.
Receive rewards
You can exchange your Soul Gems for Steam Wallet top-ups, game keys, CS:GO Skins and other rewards.
I'll pick Rengar i just like him and i think he's way more OP than K6 but i guess they are like the same too. Because whoever gets feed first surely will win the fight but in terms of equality no power ups or items it should be rengar who's your's?