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.
Although Roblox is a really good game, where you can just let your creativity out, and be yourself, I really don't like the tagging system and some of the toxic community.