Before you begin, you should know that Gramps does not
store your media, it only stores a link to where the media is on your
hard disk. So decide where you will store your pictures, videos, sounds,
and documents. Then on the menu bar select Edit->Preferences and the General tab. Set the value of Base path for relative media paths to this directory. Click on the Close button to save your changes. Keep your media documents well structured in this directory.
Per the reference above my docs are stored not in Gramps but on my drive. If one is sending a GEDCOM to someone else, How are the referenced docs transferred ? Seperate file, Google Drive?