I would not say that one webinar is more important to view than the next. There is something to be learned even from the shortest web series available. It is the content that matters here. You are trying to learn from the exposure of others in the field so, go ahead and do that through various webinars. Sure you can focus on certain topics you feel you need help with, but by doing so, you might accidentally miss out on relevant and unexpected content in the other teaching series. Learning cannot be done on a need to know basis. Specially, not when you are preparing to take, and hopefully pass a certification exam.
The opinions are that of the author's alone based on an individual capacity. Opinions are provided "as is" and are not error-free.