I see the Kettlebells Halo as a breathing/core exercise - to start go slow enough so you can pay real attention to the details of whats going on. Are you breathing continually? Are you staying tap with minimal movement? Go slow enough so you can notice deviations, tensions or breath holds and have time to do something about it. Tweak and adapt as you move the Kettlebell.
Initially I instruct people to take as many slow breath as they can for each halo - emphasising breathing and speed over repetitions. Quality is paramount fro this exercise.
Weight wise normal sized guys should try a 16kg 'bell and girls a 12kg. If in doubt start lighter.