i found that the best way for me was by killing the PIRATE boss, inside the rocky cave where several pirates are, cause you dont need to search for him, like the kozac (the one on horse), just stay there, kill that boss, wait for him to respawn, and go again (its even better/faster if you have a high level char to do it then send the gem by trader)...but do it while you're doing something else at the same time cause it will get 'BORIng'