Your Background and skillset
This is important one! What is your background? Have you got any teaching experience? Are you already a health and fitness professional? Have you got sound understanding of anatomy and movement?
Newbies would benefit from more lengthy and comprehensive, possibly face to face course that allows you to learn the fundamentals and build foundation at slower pace. Or perhaps you could consider an intensive online course to kick start your Pilates career faster if you are well seasoned movement professional.
We dare to say the real learning starts during practice teaching with clients and after your graduation. It is up to you how much effort and energy you put into your new career.
Learning never stops. Find a mentor, attend further education courses and workshops, teach and gain experience through trial and error, listen to podcasts and read the books. At the end of the day the hunger to grow and better your skills will shape you as a Reformer Pilates instructor.