Personally, I avoid social websites like the plague in the conventional sense. I’d also avoid forums. You need to really find niche ways to market yourself. i.e. Someone who stumbles upon you outside of Fiverr shouldn’t stumble upon you because they are in a place saturated with people screaming “buy my Fiverr gig.” They should stumble upon you in a place where they least expect to be impressed by you but find you anyway and say to themselves, “mmmhh, I think I’m going to bookmark this bloke.”
How you find a way to do that will be a challenge. I have been very lucky but I have also got myself into a bit of a marketing hole by having 2 different freelance identities which I can’t really reconcile.
If you are into videography & editing, enter some competitions. Write reviews for software, answer questions on Quora. I use Linux and recently submitted my story of using Linux as a freelance writer (and why it’s so much better than Windows) to an online Linux magazine.
If you want to market yourself well, you shouldn’t ask for advice as all the advice you are going to get is going to be recycled, ‘use Facebook’ garbage. Market yourself by finding niche ways which no one else has (so far) to say why you are a real authority in regard to what you do. - And get used to the fact that marketing yourself can be a full-time job in of itself.