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.
There was a great combat game called rogue lineage. it costed quite a bit of robux but was a very fun combat game. It is still up, but descended into toxicity and the moderators are bad.