One effective way is to have a website dedicated to your service(s) and advertise that website in Facebook or Google or Reddit or Twitter or LinkedIn, etc based on your target audience (your targeted potential buyers).posting my ads
All in one SEO marketplace tips , given by this user . I recommend if you have budget go with website and ads , they really work well over .Like a gift site? Seoclerks, leggit, bhw market place and build you site and gmb, rank and offer services/products to people who contact you. Run paid ads on fiverr, Google and Facebook.
And that's exactly what i said i don't want in my thread xDUpwork is unlike Fiverr because, in Upwork, the client posts a job, and then freelancers bid on that job.
SEOClerks is similar to Fiverr.