As of the present you may start off as either a Soul, an E-ranked wanderer, a Student of the academy, a D-ranked shinigami-in-training, or a Hollow, a D-ranked devourer of souls. Students start off with an asauchi. In order to promote to a C-ranked shinigami, you must have two evaluated threads in the academy and, once those two are done, one evaluated thread with the academy instructor.
Hollows and quincy will become available as more people join the site to prevent spreading the population too thin.