Stats are meant to be a means for a player’s choices to have long-term consequences. Choicescript was designed to include stats so that you can, as Dan Fabulich put it, write a long interactive novel that doesn’t suck.
The classic Choose Your Own Adventure books by R. A. Montgomery had a lot of fail states in them (often in the form of sudden, unexpected death) because it was the only way to keep the story to a manageable size. If Montgomery wanted a choice to have an impact on later events, he had to dedicate an entire branch of the story to that choice. Stats would have let him avoid that problem.
I plan to have as many stats as it takes to accomplish that goal, and no more. Your MC has a chance to practice a little shooting. Is this the sort of story where it matters whether the MC practices with a rifle versus a pistol? If so, you want to give the MC a choice, and separate stats for each. If not, you can just have a stat called Shooting, and give the MC a choice to do something besides practice shooting.
The Shooting stat tracks how much the player’s choices have reflected a desire for the MC to be a good shooter. Alternatively, the Pistol and Rifle stats track how much the player sees the MC as a gunslinger, and how much the player sees the MC as a sharpshooter.
So which stats to use and how many will be different for each game, but keeping that focus on player choice might make it easier to think about stats.