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.
As it is said (at least in Russian localized "variant" of the GameHag), writing comments in "General Discussions" forum won't give any Exp to users. However, I gaines 1-2% Exp after leaving a comment on one of its topic.
Thank you for it, but if the restriction for gaining an Exp on that forum really exists, so maybe it was a bug and it should be checked?..
If it's okay, sorry for my suggestion, I just wanted to check whether the things are all right. Thank you!