None.
'G' means no aperture ring.
Gold ring 'means' nothing really. Just decoration. G has nothing to do with gold, only the aperture being internal and controlled by the body. The PCE lenses have gold rings, and they are not G lenses.
You could say the gold ring means 'premium' or 'professional', but there are plenty of nikkors with the gold ring that I wouldn't hold to that standard.