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.
(By "Guess" I mean the Guessing Game, of course.)
Um... Imagine a situation that is infrequent but possible. A user wins a certain number of SGs through the Guessing Game, then he orders a prize. But the site (or other users) may soon mistakenly perceive this user as suspicious, since the SGs won by him are not displayed in his profile page. As I understand it, such SG is not taken into account when calculating the total number of SGs, so the total SG amount this user have ever had seems to be lower than the cost of prizes he have ordered.
Basically, the title of the thread already briefly describes my suggestion. I could not formulate it very clearly as I wanted to be brief this time, but I hope everything is fine. If a similar thread has already been suggested here, forgive me for repeating it.
Thank you very much and have a great day!