You are being very obscure in details... Tell us more please.

Could you add the output of the following info :

# emerge --info

Specify if you installed Xorg, what version, etc.

Did you read the howto about gnome ?
http://www.gentoo.org/doc/en/gnome-config.xml

I suggest you read it. There is much documentation.
And gentoo is complex to correctly install.

I used gentoo before, but now I use Funtoo. Funtoo uses more recents packages
and is more stable. Daniel Robbin, the gentoo creator, is working on Funtoo
now. But you can stick on gentoo for now it is a good distro for one that want
to learn.