I create Wikipedia pages for clients on popular freelance websites and have been quite successful with nearly 100 5-star feedback reviews as well as an overall 5 star rating... however, these freelance websites charge me 10-20% of the revenue depending on each site. Although I have started a basic pricing page on my own website, I'm not sure how to take it to market as this is a very specific niche - simply using Google or Facebook ads will not be that useful. Companies, individuals, products or topics eligible for Wikipedia are the ones with some kind of news coverage or references from published books, magazines etc. Any advice, on a general approach or marketing strategy (ads targeting etc?) and marketing venues that can be used would be appreciated.
As Nicolas rightly says, LinkedIn is where your clients are likely to be found – not Facebook or Twitter.
That said, I wouldn't pay to use LinkedIn ads in this case. Not initially. Your target niche is quite narrow, and LinkedIn's targeting might be far too broad. Compare your own ability to home in on likely clients using LinkedIn to the shotgun approach of LinkedIn ads. And also consider whether someone is more likely to respond to a hand-crafted message or an ad. Before you pay for LinkedIn ads, test your own ability to get leads from LinkedIn through your own manual efforts. If you cannot, then LinkedIn ads cannot. If you can, then you may still be more efficient than LinkedIn ads.
Apart from that, the main strategy I'd pursue (in your shoes) would be SEM. That might mean PPC ads in Google and Bing. It should also include some intelligent SEO copywriting to ensure that you're indexed and can be found organically. That's something you – as a writer – can figure out and accomplish on your own.
If you'd like advice on branding, naming, and domain selection, then talk to me.