If I was you, my starting point would be to get a cracking good website for myself. (Unless you're an absolute whiz at website design, leave it to a professional. I design websites for myself and others, where it doesn't matter if something might look a bit amateurish occasionally. However in your situation it's essential that everything really is top notch).
Then, when advertising your skills on freelancing sites, always include a link to your own website. If that looks really professional, people will start to take you seriously.