Identify your top 5-10 most engaged users and help them become more involved with the company as brand ambassadors offering perks that make them feel valued and appreciated.
In my experience, we have been able to grow our travel company mostly via word-of-mouth by focusing our resources on those clients that have shown high interest in becoming more involved with the product/service.
Happy to chat further about this.
Good luck and have fun with it!
-Cesar