Since the general storyline behind Gemfire is fairly limited, there is little room for the kind of drastic changes seen in such illustrious ports as FFIV to FFII.  (Nope, not bitter...)  However, there are still changes to be seen between Royal Blood and Gemfire.  You can also check the complete list of name changes between Royal Blood and Gemfire.

• As in the DOS port of Gemfire, Erven is ruler of Tordin rather than Gweyn.  [1]
• The Tordin coat of arms is changed, and can be seen in Gemfire as the "hidden" family of Lynotte.
• Chylla appears wearing a red bikini instead of a dress.  (Somehow I'm not surprised they changed this, since it is an early 1990's Nintendo we're dealing with here...) [1 , 2]