What do you need to plug into the USB hub? If there are several devices, or any of them draw a lot of power (e.g. external HDD), you should get a powered hub. If you just need a few data cables for connecting to other devices, an unpowered hub is probably sufficient.
Nobody can answer that question unless you tell what you wish to attach.
If all you want is USB, Anker has some nice USB hub with 3 charging ports and 7 normal ports. Obviously it's powered.
Be careful and read any offers very carefully, because some sellers think that a "USB-powered hub" (a hub that takes its power from the USB port of your Mac) is a "powered hub" (one that connects to a power outlet).