Roll my own theme or customize an existing one [closed]

You might look into the concept of using child themes to roll your own theme. A framework like Genesis comes out with regular updates and has a starter theme that can be quickly built upon.

I would take the time to roll your own so that you can know the ins and outs of your own website. If you tweak an existing theme that has bloat you may have things break later and find that fixing issues is more of a headache.

There are different frameworks and starter themes out there that will be better to start with than Twenty-Twelve.

Here is one example: http://html5blank.com/

There are also responsive ones available like this: http://themefortress.com/reverie/