I just gave Gentoo a shot tonight and got exactly the same error message.
Emerge ...... any app here will make this error aslo so will
emerge --sync or
emerge -p ....
What I did was move into the /var/lib/ directory and did a ls.
This did not return the portage/ directory emerge was looking for so I did
than ran
to redo my ports.
I believe the problem was that when I did the install somehow I lost my /var/lib/portage/
I now have it working and am starting to emerge my SSH.
(Sorry if I got confusing, it is late and Gentoo has me squinting my eyes)
Eric