Personally, I would just try and install FreeBSD and Xorg, and a couple of utilities to start with. I'm lost without Midnight Commander. You favourite editor would also come in useful.
pkg install -y mc emacs xorg drm-kmod
Is what I normally install, although drm-kmod might not be appropriate for you system.
That would highlight any potential problems you might have with graphics drivers, and you can get a feel for the underlying system and figure out how to diagnose any problems.
If that works out you can simply add the MATE desktop without starting from scratch.
Just thought I'd add, since you might not realise, coming from Linux, FreeBSD keeps the OS separate from pkgs.
/usr/local is where all pkgs are installed.
And if you get stuck,
https://docs.fr