Start with those who influence your audience. Target 'coaches to the coaches'...people who train speakers, etc. Leverage all their hard work at amassing a community by doing some account based marketing to those people; strike up partnerships; get some beta user feedback (and testimonials). If you have a solid product, it's a pure value add to their audience.

You can also target those communities with paid traffic and then just a matter of tweaking the metrics to make the numbers work. (Spend < Revenue)

And for what it's worth, I develop products with speakers, authors and thought leaders. Happy to take a peek at what you have and provide feedback.

Good luck!