The handbook is fantastic and Gentoo is a great learning experience - my tips are:
- setup binrepos (saves a lot of compile time)
- if using as a desktop, install a browser that has a binary package option like opera or vivaldi (or even Edge). Do not use chrom(ium) or firefox - they each take hours and/or massive ram to compile

You should do some research into using lvm - essentially one partition (pv) and named groups (vg), virtual partitions (lv's) that you can grow or shrink on demand as long as there's some free disk space still available
I like to name them by os + drive type, e.g. volume group names for you could be "mintnvme" and "nobusb"