Hi there, I think this is a very common mistake people make. They start using linux, pick an entry-level distro (nofi!), then look further, and see the 'prestige' gentoo users seem to enjoy, and think 'wow that would make me a pro too'. It doesn't. Gentoo, IMHO, is for people who want to make it themselves difficult. Experience shows the compiler optimizations make a minimal progress (sometimes they even turn out to be negative, in the case of some i686 optimizations).
Anyway, to work your way up the distro ladder, first try Slackware. If you can master Slackware, you know how to work with dependencies, how to configure your system in text mode, how to work in text mode. Trust me, none of the distro's you used till now rely on that extensively enough to give you a bit of the background you need to a smooth transition to using gentoo (or slackware).
I think a stage 3 is best to begin with. After that, you can always try the 1st stage install

. AFAIK Gentoo docs should be extensive enough. I used the Gentoo wiki often for configuring programs and tweaking. I don't know if printing out the full manual would be useful though... I once printed the full SuSE manual, very interesting, but nothing about the internals of linux

. Surely the Gentoo docs will contain a lot of highly technical info you might not need when installing or customizing your distro.
A great advantage of Gentoo is you have to install only what you need. But the same goes with Slackware - just select the packages you want - or any minimal distro (Zenwalk for example, sure there are others out

). It is better to start from nothing (or very few) than from much and cut that down.