Build strength in the major muscle groups that will support your inversion and arm balancing practice: the shoulder girdle, the abdominals, the hamstrings and the glutes. Practice is framed around a one arm/one leg variation of dolphin pose from Forrest Yoga called Dorsal Fin. I don't actually teach any inversions in this video -- it's really all about building strength to get ready for them.

Having two blocks would be great, but you can get by without them if you don't have any available.