I would like to practice installing Gentoo from scratch since I like the idea of the distro, but I’m quite new to Linux at all and only had experience with Debian. I suppose my very basic knowledge of terminal isn’t enough to install Gentoo, even with the handbook. So, what would you recommend to learn or practice before I actually try installing Gentoo? Also, any specific tips on installing Gentoo inside a VM?
Gentoo, along with arch and their derivatives are more advanced distros, that will require you to actually learn stuff to be able to use them.
That said, if you are motivated and have the time there is no reason to not try, and the arch wiki and installation manual are in my experience very good at explaining everything you need to know on the system side.
I know that the gentoo handbook is also very good, and the main difference between gentoo and arch is that there is the additional uncommon step to build everything from source, kernel included.
You could go with gentoo directly, but since you seem searching for a progression I do recommend to try arch first before going to the gentoo endgame.
The process of installing gentoo and arch is nearly identical. Really the main difference between the two is that arch (usually) offers binaries to install while gentoo prefers that you compile things (though it does actually allow you to use binaries as well).