Having an online portfolio is important but even more important is that you have reviews. You can put them directly on your portfolio site and they will act as 'social proof' enabling you to convert more jobs. Since you say that you've worked with computer graphic for years I assume you've done some work for clients. I bet in your e-mail you have these reviews just sitting there hiding from past clients or even associates or friends who have complimented your work. Publish them out there for prospect to see.

My portfolio is pretty weak relatively I think but more than anything when I link people to my reviews on codeable or my linkedin profile they instantly trust me and pull out their wallet :)

Outside of that another tip would be to specialize. There are lots of Graphic Artists out there you need to specialize and differentiate yourself. There are many really talents Graphic Artists out there who are successful without having a degree so don't let that hold you back.

Hope that helps. Cheers - Raleigh