Ok I lifted this map when I was snooping around in Greg's hut at the pirate camp. Apparently he has buried treasure all over the place. I've noticed a few red letter X here and there, and I assume those are the marks on this map, but so far I only dug up the one connected to the golden compass quest. Should I wait for a quest to dig up the other ones or can I just go dig up any and all of it whenever I find them?

I can be mistaken... but I think... the rest are purely items, nothing really quest related? If you can check them, then do so and see if there is anything important. And, as always in Gothic series - save often. If there is - just load the game. :)