There are two options to creating a website CMS. The first is to create it yourself. This however will require you to posses a good knowledge of web languages. This isn't an impossible task, but not one I would recommend. The other option is to use an 'off the shelf' system, such as Drupal etc. Each has its own strengths and weaknesses and really I can't recommend one over the other. I personally use Drupal for one of my sites and think it is exceptional, but that just my opinion and is based on the way I use it. There are two more options in the 'off the shelf' option. You can get a 'free' system, (Drupal) or you can purchase a system (ExpressionEngine).
The best way to get an idea on what you want is to try each 9of them out for yourself. You can do that at this site:
http://opensourcecms.com/ OpenSourceCMS allows you to test most of the CMS systems on the net. You can also test other systems such as blogs.
Hope that help,
Marzar