I manage my teams website (
warlocks1507.com), and we use wordpress as a content management system. We took our old hand coded html and css template and converted it into a wordpress theme. I would recommend wordpress, as it has worked well for us.
If you are just beginning web design, I would recommend using an existing theme rather than creating your own. Creating your own theme requires knowledge of PHP and the wordpress template engine, and gets tedious at times. Although if you are up for a challenge, go for it!
If you are looking into creating a static html site (one that isn't powered by a CMS like wordpress), you might want to explore different frameworks such as bootstrap. Bootstrap (
getbootstrap.com) is a responsive html and css framework for creating responsive web sites.
You should also check out
freewebtemplates.com. I've been able to find some pretty good templates on this site for use in some other projects.