"Social media" is a fairly broad term - a platform that enables people to connect and share with others. Hypelance would fit quite snugly into that category.
Paid advertising is indeed the way to go, however, Hypelance is a community project of mine which doesn't garner much profit. We depend on the goodwill of others through our Store to keep our servers up, hence I cannot depend on huge amounts of paid advertising simply because Hypelance does not have the financial support to do that. One thing I do want to make clear is that Hypelance will never take a commission cut of any work done here unlike other freelancing platforms. Instead, I'll probably choose to opt to monetize the site by community sourcing ad slots and other non-intrusive methods, but that means Hypelance will always work with a more limited budget than other platforms.
I mainly use paid advertising on Reddit as users over there are already familiar with the concept of "community' and discussion, making them quite in line with who Hypelance wants. LinkedIn on the other hand is indeed a very good audience, however, LinkedIn also is a very expensive platform to advertise on with an average CPC of $6.50 which is grossly too much for what I am looking for.
Facebook ads on the other hand... I have not dabbled too much with the platform. There's a lot of controversy nowadays with Facebook and I really haven't cared much for it. I'm not sure if Facebook is superior in terms of value what Reddit and sometimes Google brings me (CPC and relevancy). It could be worth looking into.
I like being transparent about these sort of things. It feels better to share ideas with the community.