Hiya! I wanna get into Gentoo-based distros at some point, would it be a good idea to run Sabayon for a while to get used to Portage and everything, before going into Funtoo or pure Gentoo, or would it be better to just jump right in to Funtoo or pure Gentoo without running Sabayon to familiarize myself with Portage first?

Hardware that either distro would be installed on would hopefully be something with an i5 and 12GB RAM at the least to maximize compile performance.

This Sabayon and eventually Funtoo or Gentoo machine would be run alongside an i3 build running pure Arch.

If it's for a learning experience I'd go for bare bones Gentoo rather than distributions based on it.
The install media doesn't contain everything you need as you pull it down off the net as required. I have to admit it's been quite a while since I did an install but I learned more from it than I have from glossy easy install distros.

Download the handbook first and check it out, excellent documentation. I found it easier to print it out.

My main reason for picking it was that I wanted a Linux OS I could install on an old Sun Ultra 2 running a couple of 400Mhz, 64 bit UltraSparc II processors and 8Gb memory.
If I remember correctly, the kernel compilation took the best part of a day! I'd to run it several times as I'd invariably miss something from the config file and, on one occasion, found the SCSI controller hadn't been included so it wouldn't boot!

Ah! Fond memories...

Play Bonny!

I agree with the above, having dabbled a little with Gentoo some time ago.

If you are looking to be more familiar with Portage, the main Gentoo will be much better than something like Sabayon as by default they cover it up with a frontend for noobs.
Similar to how you have learnt pacman in Arch, you will find Portage to be similar in use although very different in execution.

have fun

The only way to decide what is best for you is to try them. Gentoo has been around and I think it is a great distro.

I'm learning gentoo too. Thanks to the handbook I managed to install it.
There's still a lot to learn but as far I can only say it's worth it.
There no success without initial struggle

Just keep in mind Gentoo is not a distro, it is a bunch of tools (very good ones!) which help you to build your own distro. If your Gentoo runs slow it is your fault, because it is your build. Want to surpass Ubuntu? You have that chance with Gentoo, but it will be marginal. Because Ubuntu developers are professionals. Your advantage is you build the distro for your hardware - and for your hardware only. This eliminates unnecessary code and gives you slight advantage. But you have to be good to capitalize on it.
But then again, it is lots of fun and once you get familiar with Gentoo you'll realize there are ways to manage tens and hundreds Gentoo nodes without breaking a sweat.

Just go with Gentoo proper. The handbook is top-notch, and will guide you where you need to go. And the forums are great.

Having said that, I would choose Calculate or Toorox for a closer-to-the-base experience, over Sabayon.

Going for Calculate could work too, as it just uses straight Portage like Gentoo or Funtoo, however it doesn't have the hassle of setting it up that Gentoo or Funtoo has initially, so it might be a better way to dip my feet into the pool before diving right in than Sabayon, and it would be closer in migration path to how I plan on going to pure Arch: upgrading from Archbang.