There's been a few freelancer websites I've looked at over the years, but I've rarely been impressed with the results when searching (especially when it comes to art, but that's another story)
My vocalist and cellist both were found via Fiverr and were very valuable to my project. It was my first experience using Fiverr and it left a (false) positive impression. Using Fiverr some more, I quickly became unsatisfied with the results for the price and (low) quality work. Part of this reason I believe is that Fiverr and other similar sites like it require projects to have a deadline. I'm sure this ensures the contract workers won't slack off and deliver a product months later or never (which likely helps reduce the number of dispute tickets generated by users), but as a result, I think the freelancers feel more pressure to deliver something, even if it's low quality.
So far, I have had more success finding work from people just by reaching out to them on their platform of choice (for example, yourself. Though your work for me isn't finished, it's so far been a more positive experience than Fiverr).
I think having a publicly accessible portfolio along with making it known you're available for work is the best way to get contract work. Promote your portfolio and get your name out there and the people will come.
I found my current artist through this method and I really couldn't be happier with her work, especially for the price.
edit: way late edit on this post - I just re-read it and noticed the severe number of typos. I wrote this on my phone, sorry about that. I fixed some of them.