Firoz,
There is no particular reason to study the PMBOK or watch the PrepCast videos in the chapter orders.
There is a certain logic in how the PMBOK Guide is set up. For instance Scope, Time & Cost are first, because this is often a primary focus of our sponsors and stakeholders. But other than this "soft logic" it really doesn't matter how you study.
Here is my recommended order in which you can watch the PrepCast videos and study for the exam:
E00.00
E00.01
E90.xx - Watch these early on so that you learn all about the basic of the exam.
E01.xx
E02.xx
E05.xx
E06.xx
E07.xx
E08.xx
E09.xx
E10.xx
E11.xx
E12.xx
E04.xx - Watch integration later so that you know what it integrates
E03.xx - Listen to these and try to answer the questions asked for yourself as you listen. Make this a challenge to yourself.
E80.xx - Listen to these last, so that you can now make the connection between the real life examples and the theory in the PMBOK Guide.
However, I would say that you can "mix and match" E05.xx - E12.xx and watch them in any order that you like. They are separate topics and can be watched in the order that you prefer.
Until Next Time,
Cornelius Fichtner, PMP, CSM
President, OSP International LLC