As mentioned, course difficulty is a significant factor as is the shooter's understanding of their true skill level. A typical duffer will probably range in the 40 percentile on a charity event type course on down to the 20 percentile on a more challenging registered course. At least that is what I've seen over the years.
What is more important than score is using the opportunity to analyze your performance as to your strengths and weaknesses then improve on them. This will improve your shooting in the field and on the course. The quickest and cheapest way (in the long run) is to take a couple lessons with a good instructor. The price may seem high but you will learn far more than what you learn from a similar amount spent on shells and targets.
As also mentioned, like every other shooting "game", sporting clays has morphed away from its original goals. When I started shooting sporting clays, quail walks were encountered and the duck tower was commonly shot sitting in a boat mounted on springs among other things. Needless to say, those presentations went away for safety reasons which was not a bad thing for the sport. But, the skills learned on the clays course carries over into the game fields and one will not be worse off learning to shoot better.
