I cannot recall ever seeing new folks show up and get laughed at, and I've been shooting a bunch of IDPA the last couple of years. The more experienced regulars would/should shut that attitude down pretty quick. We all start somewhere and whether folks show up as new shooters or just new to IDPA -the only standards you must meet involve safety. In fact most of us would prefer a new guy go slow the first few times out so we can confirm those safety standards are understood and followed.
Now to try and answer your question, it has a lot to do with the club -but I think most folks can make Marksman even with minimal round count and practice. One's age and health and prior handgun training obviously will greatly influence the starting point and how hard it may be to climb the ladder. But most Marksmen who know the rules and start learning the game will look fine and can enjoy the match just for the shooting and even focus on the defensive basis of IDPA.
If the competition gets your juices flowing then you can still push yourself to Sharp Shooter with low monthly round count (100 or less) by practicing the non-shooting movements at home. Smooth reloads, lotsa dry fires, and a smooth (safe) draw -just to name a few.
BTW, there are plenty of Marksmen shooting at the big time sanctioned matches. Sometimes folks overlook that its really at the larger sanctioned matches that the whole Division/Classification system starts to make sense. At local clubs you may not ever have more than 2-3 shooters in the same Division/Classification. But at the big matches you actually get to compete with a larger group who are generally on your same (current) level. -Well until those dirty rotten SANDBAGGERS showup
