Is this Funtoo 1.3 or 1.4? Because in 1.4, there were some changes to how video cards are configured. Notably, a static VIDEO_CARDS declaration in make.conf is going out of style in favor of mix-ins. If this is 1.4, then comment out your VIDEO_CARDS, and make sure the gfxcard-nouveau mix-in is enabled.
https://www.funtoo.org/Make.conf/VIDEO_CARDS