Board Thread:Roblox help and discussion/@comment-25463843-20180509205826/@comment-26397550-20180509212740

Game cards offer a set amount of Roblox balance that can be used to purchase Robux or forms of Builders' Club. The $10 card gives $10 of balance, etc.

The most immediate ways is to order a card online through a service that will email you the code (Walmart does this for example) or link a credit card