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.
For my opinion doing surveys is the best way to collect soul gems cause I am bored of playing online games. What do you guys think pls tell me