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.
After just a short look at the gems to cash/ skin value conversion. Its not worth it to trade gems for csgo skins. Just buy the steam gift card, for REAL. Go calculate and good luck guys!