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.
I've been told that one of the Gamehag admins was banned from Roblox, so they're trying to sort that out. It's likely also due to legal issues. You can still buy the ROBUX Giftcards.