These days I think the best approach would one that uses a Responsive Theme. That means one that was built from the ground up with smartphones in mind. These are adaptive themes that display images and layout appropriately based on the device that a visitor is using.
It is a design philosophy that is really impacting theme design this year. Here are a couple of links to get you started in the right direction on this (both list free themes from reputable sources). Most, if not all of them, are available in the theme repository.
https://www.webdesignerdepot.com/2012/08/15-free-wordpress-themes-to-get-you-started-with-responsive-design/
https://wpmu.org/16-beautiful-and-free-responsive-wordpress-themes/
Also, keep in mind that the new Twenty Twelve default wordpress theme coming out in the next update is going to be responsive. I’ve looked at the demo of it and it is beautiful. If you are comfortable with CSS then it would serve as a great starting point for a very nice website (though if you know CSS any of those themes above would be great).
