To get started you will need a gun (pistol or revolver), strong side holster (any type, check rule book on holsters), spare mags or speed loaders and mag or speed loader holders.
I would recommend a total of 3 mags or speed loaders. (i.e. 1 in the gun, 2 on your belt)
Of cause eyes and ears.
Generally speaking, it has been my personal experience that IDPA shooters are very willing to help newbies. If you turn up at a club match, the RO/SO will usually walk you through what is needed to handle the COF safely.
GO SLOW, STAY SAFE, HAVE FUN. Speed will come with experience.