[Need Advice] Thinking of starting a microfreelancing site.

Just as the title says, I'm thinking of starting a microfreelancing site. I got this idea because I'm currently selling stuff on a freelancing site that feels very limited - we're not allowed to communicate outside the site and the main form of communication is via sending "e-mails" within the site. This slows down everything, in my opinion.

Setting it up is pretty easy because I already found a theme that has the exact same features that I envision this website should have.

Now the hardest part is the actual promotion of this site. Can anyone give me some tips and tricks on how to entice freelancers as well as buyers to use this site? Of course this includes blogging and social media promotion, but any other advice is greatly appreciated. Thanks in advance!