@Dirk@Fungus
Arch + aur is a little bit too much in my opinion. Old PC = old slow hardware. Some of aur pacages are basicly compile instructions. Also you won't benefit as much from rolling release.
For GUI stay away from GNOME as it is resource hungry. KDE claimes to be a lot better but honestly it is still a very polished flashy expirence out of the box.
Learn using KDE, atempt to replicate using window manager like AwesomeWM.
You will "waste" resource only for what is a mass have for You.