There's no secret to install the proprietary drivers for the video card, just unmask the latest version on /etc/portage/package.keywords by adding:
And then emerge it. After that you must configure your xorg.conf.
Since synaptics, display and keyboard configuration also goes on xorg.conf, I'll just upload mine to the virtual drive. Download it by clicking 'My config files' on the right bar, links section. Browse to /etc/X11 and download xorg.conf