you should probably start by reading our wiki on the package managers and how to use them.
Gentoo uses .ebuilds, using .dep and .rpm are the very last resort. You would use source before them even. It's very very rare that you will ever need to do such a thing.
If you don't understand portage than you should stick with entropy and wait for packages to come available. If you don't watch what you are doing, you will break the system easily. There is a learning curve to using gentoo based distros.
Use it as is and learn your way around - the Sabayon Linux wiki and Gentoo docs are plentiful -- viewtopic.php?f=57&t=1730
It's vital that you learn the package manager before you break it.