Here's what I recommend as a progam to develop fighting oriented weapons skills:
1. Take a fighting pistol class from a good school/trainer
2. Take Force on Force pistol training from a good school/trainer
3. Take a fighting rifle class from a good school/trainer
4. Pay training "installments" each month in the form of focussed drills, e.g. those done in class
5. Develop marksmanship/gun-handling/speed by shooting IPSC/USPSA and 3Gun matches.
Almost all the Gunsite "school drills" can be adapted to a carbine.
A few months ago there was a thread which contained a practical set of shooting tests, including box drills, mid range, and first-hits at long range.
I hesitate to say there is just one benchmark which differentiates shooters, however, IMO, basic gun-handling and operation, ability to clear jams at speed are required for simple competence.