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.
to level up fast you can complete contracts, complete tasks, play games or comment on forums, articles or games. now note that if you spam you will lose XP and commenting may get banned from your account. my friend told me that he cant comment anymore because it is blocked from his account so be careful.