It depends heavily on the CMS's (module/theme) API, for instance, one Drupal modularity in my opinion is its greatest strength, although learning Drupal itself is not to be taken lightly either. I've seen a lot of commercial sites done in Drupal, most of them look successful, but it made me think what was the total cost of creating the modules, customizing it, etc.
Since you mention you are a newbie in this stuff, do take in account all the stuff to take care of when you are creating a website from the scracth:
- Security (XSS prevention, sql injection, blah blah)
- Authentication
- A flexible theme system (unless you mix html with code... good luck, although there are some really nice template system available for PHP 5)
- Database Layer (just use an ORM)
- Learning JavaScript, then learn jQuery, MooTools, etc.
- Administration panel
- Adding stuff like content management
But most importantly, plan something before doing it. Starting out just because you feel like without planning what you want and how will you implement it creates uncertainty, just too many doubts...
So start with a CMS, even for a personal site. There are solutions like Joomla! Drupal, SimpleCMS, some django CMS are also out there. Learn the language of the CMS and start creating your own module as you see fit. Always read their documentation, search in forums before asking, or search here in stackoverflow. Really.. just ask here.. better than googling for a solution :P
