Gold ore shares node spawns with both iron ore and mithril ore, so both of those farming locations should show some gold ore spawns. They are rare node spawns, so if you are farming an area, it is best if you farm all ore nodes in the area, as they will have a chance to respawn as a gold ore vein.
Gold bars are used for transmog gear, including the Brightcloth tailoring set and Golden Scale blacksmithing set. Gold is also used to make a Gold Power Core.
Gold bars still sell well on the auction house.