If you're not currently trained in Microdermabrasion then you'd need to go on a course. Some machine providers offer training in with the equipment price. You didn't mention that you currently offer any form of skin-care, so maybe basic / product facials would be something you could look in to first?
As you already offer waxing, how about adding tinting? That way you could offer eyebrow & lash treatments, which are quick to do but quite profitable. Eyelash lifting also popular!
Or you could make some smaller changes to your current menu, like luxury versions of your manicures and pedicures i.e. adding masks, heated mitts/booties, hot oils or paraffin wax etc. or nail art if you don't already offer, like stamping, wraps, glitters etc.