Instructions
Double-click the Roblox icon on your computer to launch the gaming window, then click the "Money" option in the main menu.
Select the "Trade Currency" option and select the amount of Tickets that you want to trade for Robux in the pop-up window. Click the "OK" button.
Go to the Roblox Central Bank Web page, then select the link next to the number of Robux that want to purchase. The payment page will open where you can enter your payment information and click the "Purchase" button to have the Robux added to your account.
Go to the Builder's Club Web page for Roblox, then click the icon next to the type of membership you want. The payment page will open where you can enter your payment information and click the "Purchase" button to become a member of the Builder's Club. You will automatically begin to get Robux just for starting your membership.