Honestly, the best person to tell you where to start is your customer . . . the healthcare professional. So you actually need to start with Customer Development.
As Steve Blank says: "Get out of the building and talk to customers."
You need to actually get in touch with some of these professionals and ask them what their biggest problems are. Don't mention blogging or webinars - these are merely vehicles. And worse, if you ask if your customer will read the blog or attend the webinar, they'll always say yes, but likely won't follow through. UNLESS, it's solving their biggest problem.

Get to know your customers intimately and you'll know not only what you should start advising about but also the best method to deliver it.