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.
You can exchange your Soul Gems for Steam Wallet top-ups, game keys, CS:GO Skins and other rewards.
I have a few coins leftover I need some help choosing what SBCs and player icon swaps I should do. Anyone got any tips? Any input is thanked personally.