You do need to sanitize the bucket, but it doesn't take much. It varies, but lately I mix up a gallon of star-san in a gallon bottle of distilled water and siphon out of that into the bottling bucket in order to sanitize the racking stuff / bottling wand, swirl it carefully while tipping the bucket, and then drain it through the spigot into another bucket (I also spritz thoroughly on the part of the bucket where the washer makes contact for the spigot). Then before racking, I use my spray bottle to thoroughly wet the entire inside of the bottling bucket and pour out the excess, and the rack.
As cheap as star-san is, though, I wouldn't fault anyone for using too much. In my case, my water is hard enough I don't trust it for sanitizer, and I don't like buying more distilled water than I have to, so I tend to use it slightly sparingly.