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.
Personally, I love the new ARURF Game Mode version with all the champions and it gave me the opportunity to practice some champs I couldn't play before (even though I just spammed xd). What's your opinion about it? Is it the best Game Mode for you, too?:3