The correct answer is the one closest to you.
Both IDPA and IPSC/USPSA (USPSA is the governing board for IPSC in the USA) are very receptive to new shooters. So is NRA. Everybody has to start somewhere and every organization depends on new memberships to grow.
Many clubs and ranges will have a new shooter orientation program or will assign you to a mentor to explain things to you.
But when the shooting starts, everybody gets the same targets. In an action sport like IPSC or IDPA you will be cautioned to not run before you walk, literally; but the CoF (Course of Fire) requirements are the same for all. I know of no shooting sport with the equivalent of a "bunny slope" for beginners. At most, some IDPA clubs will not require you to wear a concealment garment until you are sure you can make a safe draw from under it. A few ranges will allow (or require) a beginner to start from a ready position with gun in hand until he has demonstrated that he can make a safe draw in the first place.
The best thing to do (short of paid professional training) would be to get acquainted and get a coach or experienced mentor to run you through some exercises. You cannot learn to shoot at a match. And by "shoot" I mean more than just aim and fire the gun. You have to know the range safety reguirements, you must be able to load, holster, draw and fire, move to another firing position, fire on the move, fire from different positions over, under, around and through range props, fire with either or both hands, reload rapidly and safely, shoot some more, then "unload and show clear." IDPA and IPSC match stages are seldom the same from match to match; I have never seen a whole match repeated. So you have to be able to pay attention to instructions and remember what you are to do.
My priorities are:
1. Be safe. Don't hurt anybody, don't scare anybody, don't get disqualified for violating a safety rule.
2. Execute the CoF. Shoot the right targets in the right order, don't get lost on the course and don't get procedural penalties.
3. Hit the targets, hit them in the middle. 'Nuff said.
4. Move right along. Your time is your score (in IDPA, IPSC is more complicated, but it is still a major factor), assuming you make the hits. Don't go faster than you can safely, correctly, and accurately perform, but don't dawdle.
Your guns are suitable for IDPA Stock Service Pistol and Stock Service Revolver; and for IPSC Production and Revolver Divisions. You need a strong side straight draw holster, a magazine/speedloader carrier, several magazines or speedloaders, ammo, eye and ear protection.
For NRA, a good .22 like a Buckmark or Ruger Mk II Target would get you off to a good start in the smallbore portion of the National Match Course (bullseye.) You can shoot smallbore for a long time before getting into centerfire, big bore, and service pistol The CoF is simple and standardized, but if you are determined to do well at it, in no way easy or boring.
