This is a great starter on speedlights! I am looking into getting set up with 3 or 4 remotely controllable lights, possibly YN-560 III’s, along with the Yongnuo YN-560-TX controller. How you like it?
One more comment: if the flash is your main light source, adjusting your shutter speed will not affect the exposure much because the flash sends all that light out really fast. Adjusting the aperture and ISO will have the normal effect.