It's thanks to Gentoo that I've been a Linux sysadmin for over 20 years.
That being said, I've since moved to Arch and then Debian.

Some points:
On modern systems you won't really notice any speed improvements from custom compiling the packages. Apart from maybe some numbers in articial benchmarks.
On old systems with very limited resources, you can eke out a bit of more performance.
Back when I was still using Gentoo, my proudest moment was getting a Pentium 1 with 96MB Ram (Yes, MB!), which was a gift of a colleague to his broke brother, into quite a useable little machine. Browsing, listening to MP3s, email, some simple games.

I also noticed a noticable improvment in performance in a 400mhz Athlon I had setup for my mom.

That being said, I was only able to do this, because I was using distCC to distribute compiling across several machines to keep compile times to a somewhat sane level. Also, I was doing a unpaid internship at the time, so I basically had all the time in the world, so compile times didn't really bother me.

I had tried to use linux before. After Windows XP crashed one too many times. I decided to see how things work on Linux. I initially chose a "easy to use" desktop distro. (Mandrake Linux). Got everything setup. Even 3D Accelaration worked. Everything was really nice and fun. Then I tried to tinker under the hood and I broke something that I couldn't figure out how to fix. So I thought, maybe I need to find something even easier, so I chose Suse Linux.
Same story. Set everything up. Desktop working, 3D working, etc... start to tinker, break something, back to square zero.

Then I decided to change my approach and choose the hardest distro. The choice was between Linux from Scratch and Gentoo. Linux from Scratch sounded waay to painful, so I chose Gentoo.

It took me 3 days until I had a somewhat working system without a desktop. Then another 3 days until I had a desktop running Fluxbox.

But the learning experience was invaluable. Being forced to use the CLI and not only that, but more or less configure everything by hand. It takes aways the fear of the CLI and you get a feel for where everything is located in the filesystem, which config files do what, etc... It demystifies the whole thing substantially.

You suddenly realize that nothing is hidden from you. You are not prevented from accessing anything or tinkering with it.

The downside is that Gentoo takes a lot of time and effort to maintain. But the learning potential is invaluable. Especially if you use it to also start doing little projects in linux. e.g. File server, router, firewall, etc...

Me knowing Gentoo, got my first real job as Linux Sysadmin and before long I was training rookie Admins. And the first thing I always did with them was to run them through the Gentoo bootcamp.

Once they go to grips with that, everything else wasn't that difficult.

Take your time with the install process. It's possible that you may breeze through it. It's also possible that you may discover that, say, there's something wrong with the EFI implementation of the system you're installing to that you need to do some research to resolve. I've had both experiences.

Once installed, Gentoo is pretty much rock-solid, and almost any issue you have can be fixed if you're willing to put the effort in. Portage is a remarkably capable piece of software and it's worth learning about its more esoteric abilities, like automatic user patch application.

Do take the time to set up a binary package host. This will allow you to install precompiled versions of packages where you've kept the default USE flags. Do everything you possibly can to avoid changing the flags on webkit-gtk, because it is quite possibly the worst monster compile in the tree at the moment and will take hours even on a capable eight-core processor. (Seriously, it takes an order of magnitude more time than compiling the kernel does.)

Install the gentoolkit package—equery is a very useful command. If you find config file management with etc-update difficult to deal with, install and configure cfg-update—it's more friendly.

If you're not gung-ho about Free Software, setting ACCEPT_LICENSE="* -@EULA" (which used to be the default up until a few years ago) in make.conf may make your life easier. Currently, the default is to accept only explicitly certified Free Software licenses (@FREE); the version I've given accepts everything except corporate EULAs. It's really a matter of taste and convenience.

Lastly, it's often worthwhile to run major system upgrades overnight (make sure you --pretend first to sort out any potential issues). If you do want to run updates while you're at the computer, reduce the value of -j and other relevant compiler and linker options to leave a core free—it'll slow down the compile a bit, but it'll also vastly improve your experience in using the computer.

(I've been a happy Gentoo user for ~20 years.)

Gentoo is very much like an manual transmission. If you ask anybody that drives manual they will say 1 of 2 things "i like it because it gives me control" or "i use manual because i always have"

I love gentoo as playing around and trying stuff out. My personal recommendation is use ZFS or btrfs for a file system and have subvolumes. So if you get so lost in the rabbit hole you can climb back up.

If your philosophy is" stable and mine!"
Gentoo is for you.
You can build a distro, with all the packages you want and once your done if you decide to update every month and dont care a whole lot about bleeding edge. It will work really well, it you want bleeding edge, you can have portage use ustable packages with a stable system. But you really must know what your doing or you WILL BREAK STUFF.

I ran gentoo for 6 months then went to debian, its a great learning tool for understanding how linux works under the hood. I would also recommended systemd over openrc.
Its not that openrc is bad, its just alot of extra work for simple things to work.

Gentoo to me is more a messing around on a spare computer distro, than a production computer. Not that it cant be production, but im personally very lazy when i just want to use my personal pc.