Buy Items - Much like selling your items, you can also purchase items with Forum Gold in the various trading forums. If you see something you like, you can post an offer on it. If later you find that you don't want it or don't need it you can just retract your offer, but you cannot retract your offer after they have accepted it.
Buy Signatures - You may use the Graphic Request Forum and offer forum gold for somebody to make you a signature. You do not have to accept the signature that the person has made for you but a little tip is always nice, although not mandatory.
Buy Guilds - You may purchase a Guild that you can manage and have members sign up for. Once you have purchased a Guild you may also purchase many other features for the Guild. You can find out more information by reading the Guild FAQ.
Buy Orbs - You may purchase orbs for your forum name, which changes its color depending on which orb you purchase. These show up when viewing topics on the forums. You can find out additional information about orbs view reading the Orbs Help Guide.
Topic Title Decorations - You can purchase topic title decorations when making posts. You can make your post title Red, Italic, and Bold. Each style costs 5 fg, and all three can be used at once.