Advertisers want to see that you have a "name" and a domain, whether it is [dot]com, [dot]net, or dot]org. Having your own domain name will increase the chance of getting more jobs from advertisers. Of course there are other things to consider when aiming to entice advertisers such as your website's traffic rank and Page Rank.
To purchase a domain name, use a reputable site like "go daddy", I am using them and have no problem so far. Or you can search online to find hosting sites that offer FREE domain name. You will find in some useful details and comments in my article FREE Domain Name very useful if you are in the market for your own domain.
And "cheers" to our very own domain.