@elendil
Depends on the source you use for GG (Geekgadgets).
If you come across one of the very first GG-CDs done by Cronus
(not related ;-) ), you could just do it by using the standard
installer.
But that version is really oooooooooooooold.
The downloadable version come with a small readme, and
after you the fist miminmal setup (BOOT.something)
running, you would only need to run a script.
Problem is you would still be missing the include-file
to compile SW that uses Amiga-specific APIs.
But that should be enough for "Hello world", and after that,
just ask again.