With WordPress and Tumblr you can create free blogs. Start with Create a Website (WordPress) or Get Started (Tumblr), the rest is self-explanatory. With the free version you are restricted to the existing domain ending e.g. yoursite.wordpress.com or yoursite.tumblr.com. but that’s fine for getting started. WordPress offers a lot of control and many free themes. Themes contain stylesheets and allow you to change the visual appearance of your blog, like font type and size, layout, colors etc..
With Tumblr you have less design options and fewer themes which makes it more straightforward to setup. Both blog types allow extra customization by editing code and scripts, if necessary.
Below you find some hand picked themes, which are suitable for showing off a portfolio. Just select “Live Demo” (WordPress) or “Preview” (Tumblr) to inspect them. Once you have registered a WordPress or Tumblr account and made at least one post you can “Activate” (WordPress) or “Install” (Tumblr) themes and instantly have it applied to your blog.
Keep in mind: Content is king. Design and themes are serving.