My view is that this is pretty much impossible with a standard Amiga 500, I mean, come on, 512k memory, no FPU, no MMU, 7.14MHz 16-bit processor. Now if you can get hold of a Viper 530 accelerator board or something similar, then maybe.
And even if you decide to give it a go, Gentoo doesn't support the m68k architecture.
Debian, on the other hand does, but only on 68020 and up.
Edit: Well, there actually seems to be a m68k profile in Gentoo as well, but I couldn't find a single ebuild keyworded for it, so it's a pretty good guess that it's completely untested.