Theme creation interrogation

hi,

I got to build a site using wordpress. The site’s structure isn’t really ‘blog like’ it’s really more like a usual promotionnal site. http://redsteelgame.fr.ubi.com/red-steel-2/index.php?page=home (this sort of structure).
I’ve never worked neither with wordpress nor php, but I know ASP relatively well.
Should I start from scratch by creating my own theme, or use an already existing theme like thematic or hybrid dans create a child theme for them? Wich one would be easier?
Thanks for your answers