Plus your idea is too broad, its a sharing platform/social network/ Shop? I don't even advice on having a sharing platform for all medias, let alone an idea this broad, which would be almost impossible to identify, contain and brand. But nevertheless i wish you the best of luck
So if you don't even have a messaging platform, it'll be even harder to compete with networks that have already been established and have significant adoption.
Also, for what it's worth, I think that in order to really compete with the other networks, in addition to a messaging platform, you're also going to need mobile (iOS and Android) clients for your network so that users can engage while on the go.
Edit:
So you're going to need all of this to achieve basic feature parity with established networks, forgetting advanced features like Google Photos, and then you're going to reach the hardest part - convincing users to switch from the network that all their contacts are on to a brand new one.
If you are going to compete directly with Facebook, and manage to get funded and build a good team, then welcome your forthcoming Facebook acquihire. :-)
I will suggest, make it short and simple.
On each product page, including links to popular statuses and articles that mention the product could increase user engagement.
For videos that show a product in use, having a "Buy This" button that tracks the number of sales each video generates could help forge affiliate partnerships between manufactures and content creators.