I got both Advanced and Instrument Ground Instructor. I believe I took the basic and instrument exams, presented both to the FAA at one time and got the AGI & IGI. Check with them as times have changed. Also, the GI ticket is good for life! I believe if you have a GI ticket and can pass 4 out of 5 students on their first checkride you can become a Gold Seal Instructor. The best time to do it is when you are doing CFI training as their is much overlap.
On the down side I believe the exams are geared to fixed-wing.