Well in my opinion it wouldn't be fair to you to focus more on one type of business and ignore others. You may never know where you can recruit strong ECA members. All advertising is good advertising. Remember as well, some people have greater success recruiting total strangers than people they already know.
That being said, you may get some ideas here: https://www.sfimg.com/Training/WhoDoYouKnow and promote: https://www.sfimg.com/Training/TCFreeListing