Generally when it's not documented I go with at least 20 GB for the os on the HDD.
Than I allocate 500M for the /boot, 30 GB for /root, and 1-2 GB for the /swap.
This guy installed Gentoo on a Pentium 233MHz with only 64MB of RAM-
https://superuser.com/questions/1264...e-requirements
When you get the chance check out the
"Gentoo Handbook".
The hardware requirements for each architecture are placed in our Gentoo Handbook, in the Choosing the right installation medium chapter for your respective architecture.
https://www.gentoo.org/support/
Good luck with your installation and enjoy your Gentoo Linux.
