I'd like to find out more about growing your audience for an online marketplace. What is the best way to approach growth?
As mentioned, it depends on what your specific goals are and what kind of marketplace we're dealing with. I know the best practices / approach we used at Skillshare, but let me know if you have a more specific question.
As the others said, it can vary but I have found that one of the fastest ways to grow an audience is to give away some related knowledge. For me, this was creating online courses to provide for free in the areas of photography and online marketing. It does not take a lot of time to do a screencast or a couple of videos teaching something and there are plenty of marketplaces for online learning that have students wanting your content. From two courses I have just shy of 30,000 students and it's still growing. Once you have a decent audience who you trusts you because of what you have taught them, you can ask them to check out your offerings at other marketplaces.
I'd strongly suggest you study this:
It's all you need to get started.
I happen to be a member of the team, so if you need further help, feel free to contact me.
It depends on your niche, industry, what your goals are, who your market is, and so on. There is no "one size fits all" answer. Feel free to set up a call to discuss your needs and get "real" answers instead of dangerously ineffective cookie cutter answers.
The beauty of a "two-sided" marketplace. I can actually tell you how we started ours. I actually wrote a post, but in essence we "seeded" one side of the marketplace with our own video courses. This built confidence "enough" to the point other authors were "enticed" to upload content to our site. Today we have more 500,000 registered students and receive about 1M uniques per month.
Glad to hop on a call and dig deeper or just read my post on how we started: http://blog.tareasplus.com/startup-leveraged-youtube-create-marketplace-500000-subscribers/
Focus on one niche and find out what your audience values the most. Then, build content around using inbound marketing. Remember, SEO rules have changed. So you can't just take content from another site and republish on yours. You'll actually lose points doing this and your ratings will suffer.