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.
This exercise has 2 purposed as I'm using it - to improve hip mobility and movement whilst maintaining core function, and freeing the ribs cage and thoracic spine to allow rotation of the upper body and shoulders.
Take it nice and easy and try to find space, rather than forcing the movement - it takes time and as you improve the various tensions should be replaced by a springy, elastic feeling and the joint begin to unlock and the tissues are allowed to lengthen.
Alternate nostril breathing is an exercise designed to train efficient nasal breathing. This reflexively create efficient diaphragmatic breathing for improved health and performance, and is the basis of all the core training I teach.