You don't really need to study anything specific to be a Bookings Editor. Many get that job after being a fashion assistant/editorial assistant.
I think nowadays having a blog can be helpful, but I wouldn't say that to work in fashion magazines, you need
a blog. The lines are blurred much more and with the likes of Susie Bubble working for Dazed, and Rumi at Fashiontoast etc blogging for Lucky Magazine has been a step forward in bringing the fashion blogging and fashion print media together, but it's still far way from being necessary to have a fashion blog. Even though those bloggers have done well for themselves now, I'm still not sure if this sort of integration will be sustained in the long run, maybe it will? Who knows