All 3 ranges are used regularly but probably calming the most, closely followed by hydrating and then re balancing.
When i bought my first order I got the kits and used the small sizes first to get a feel for which I'd use the most, then as I finished one I'd buy the salon size next.
It probably depends on your client age group though for facials. If you have more young clients than oldies you'd probably get through more re balancing products.