I've already seen so many startups building apps and products which heavily rely on user driven content, without knowing where they'll get their initial content from (a.k.a. "I'll built it and they'll come"). Almost all of them are failing because of a lack of planning how content will be generated in their product.
This mainly applies to two-sided marketplaces and social media platforms and apps, since they are kind of two-sided marketplaces as well.
One the one side of the marketplace there is the provider of goods or value and on the other side there is the receiver of value, meaning that the consumer receives the value of the providing side through the platform. For social media platforms it's actually the same, with the difference that the good which is received is content.
Importance of value providers
Having a good strategy to get the providing side to create content or value is essential because it's the thing that makes your product work. It can has various forms, it can be an apartment which someone provides through AirBnB, it can be the traditional text or article of a newspaper, a tweet on twitter, an image on instagram or a video on snapchat. It's basically the thing which is consumed or received by users.
Content can also be less obviously. It could be even less conventionally like a simple interaction. Let's take for example the the first version of Yo. The only content, which was delivered, was a simple Yo to a friend, triggered by pressing a button. So this interaction was already the whole content to be sent. No more, no less. But that was also the thing which made Yo a success. Because it was that easy, and users loved it and created tons of "content".
You see, it's essential to have users on your platform who are providers. But these users are normally hard to convince in the beginning because of the lack of the receiving side. Providers need a benefit on your platform, which is reaching an audience for either a good or content. Therefore you need to start thinking you will receive your initial content.
Basically you have two options to gain that: One way is, that you as the publisher of the app, create the content yourself. That could be an automated way retrieving data through e.g. APIs or by creating and curating the content by yourself. The other way is to let users create and consume the content themselves. While the first one (in most cases) is easier in the beginning, because you are responsible for the initial content yourself, it's much harder to scale afterwards. The second one is easier to scale, since you are not responsible for the content, but you start with less to no content at all.
Instagram, Facebook, Twitter, ... are only working because people are uploading photos, posting statuses and links actively, so their followers can see it. Otherwise these platforms wouldn't exist. If all the users would only consume the content, there wouldn't be single picture on instagram to view. So you need users, who create content or provide value.
Therefore, there must be a benefit for the content creator to take the initial step and create something worth consuming for others. For marketplaces it's the obvious reason (money), in social media the benefit is to reach an audience. Here comes the chicken and egg problem. For a new content network neither the providers nor the receivers exists. This is the hardest thing to overcome in the beginning.
At sharedspaces.at, we had this initial problem by ourselves. sharedspaces.at is a listing platform for coworking spaces in Austria. We built this platform because we thought, the benefit for coworking spaces will be big enough to publish a listing on our platform. We started this platform with zero content (= no spaces). So we send an email to all coworking spaces we knew, to create a listing with their coworking space (for free, of course). Very soon, we realized that the effort to publish their space on our platform was obviously still too high. The owners of the space didn't see the benefit of creating content for "users" (= visitors of our platform), which weren't there yet (because there was no content on our platform). Since this didn't work out, we decided to make it easier for coworking space owner. So we published the listings of the coworking spaces on our own, filled in all the content, uploaded all the pictures. Then we again sent an email to all owners, saying that we already published their space and they only have to register an account on our platform, so they can claim their space. At least a few owners signed up and we transferred the first listings. But still not what we expected. We finally put some efforts into SEO and visitors started to find our platform via search engines. About half a year later, almost all of them claimed their profile, since we were forwarding the owners of the unclaimed coworking spaces every single inquiry from our visitors. After they received the first few inquiries they finally did see the benefit of our platform. We didn't think that it will take that long but it was a crucial learning.
Here comes the catch
The first problem you have to solve is how you get the providing side. Thus, your focus in the beginning should be attracting those users, not implementing new features or adapting other platforms. If you want get providers on your platform, receivers or consumers won't come there either. Having already an providing side on your platform is a perfect place to start targeting the receiving side and in my experience a bit easier.
Try to find some early adaptors and deeply understand what their real need is and how you can improve your product to fit their need.
Build your product with a minimalistic feature set. It should really only contains the core features of your product. Not a single nice-to-have, not a "we might gonna need" this feature. But don't fuck up the user's experience when they first try it. Aim for the Minimum Loveable Product.
We made the mistake building an over-engineered platform, with features which still(!) no one needs. We thought we will need all that stuff, but in the end the only important thing were the amount of listing on our platforms, how visitors could find them and interact with the owner. We didn't test if the “problem” we wanted to solve was big enough, that coworking space owners are willing to generate content.
Also, if your product aims for different platforms, start only with one and get that perfect instead of serving multiple platforms ok-ish.