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.
Why guys, I never played crossout before, the reason is because it just seems like a game where you would be able to get bored of it very quickly an it would be to grind.