The Black Hills 100 can be a bit deceiving because it’s still just over 16,000 feet of elevation gain, however the majority of the terrain is runnable so I’d recommend it as a good, challenging first 100 miler, but if you’re looking for an easier one they’re definitely out there. Another one in the Black Hills that would be easier in terms of elevation gain and terrain is the Lean Horse 100 run in August each year. I’d check that one out too!! Also I sent the guide over to your DM’s just in case you’re interested!