Dhcpcd

Dynamic Host Configuration Protocol Client Daemon (DHCPCD) is a popular DHCP client for Gentoo Linux users.

Emerge
Use the following commands to install dhcpcd, add it to the default runlevel, and start the service:

All its configuration goes into but for most installations nothing needs to be done there, presumed that most computers nowadays are behind a router or access point providing DHCP. Though man 5 dhcpcd.conf will be helpful in case of advanced configuration demand.