Personally I believe that everybody should have to show that they have successfully completed at least a basic NRA style firearms safety and shooting course before buying a firearm from an FFL because if you can't handle a firearm well enough to do this I don't want you around me with one.
Why? Well untrained and poorly trained people with firearms, even if they're upright law abiding folks, scare and make me more nervous than criminals because they're actions are unpredictable whereas with a criminal you pretty much know what they're planning to do.
Now before someone responds with "requiring training is an infringement of the 2nd Amendment" let's take a close look at the wording of the Amendment.
One of the key phrases is, "A well regulated militia" right? Contrary to what anti firearms folks say "well regulated" doesn't mean having the correct paperwork, stamps, or approvals from some government agency. In the context of the words' use when the Amendment was written "well regulated" means organized, equipped, and trained.
Militias, especially those of frontier settlements, were the original first responders and were suppose to respond to everything from attacks by Indians and criminal bands to floods, fires, or helping an injured or sick neighbor get in or harvest their crops.
In order to be effective they met regularly with someone in charge so they were organized to a degree instead of a mob and each militia member had to have a firearm and a certain amount of lead and powder and had to be competent with their firearms.
Organized, equipped, trained.
Since a lot of folks, especially in the frontier areas, still hunted for food and furs back then being competent with firearms was important for more than just defending yourself or your community.
I started shooting almost 70 years ago when I was 5 but before I ever touched a firearm my father; a hillbilly from SE Ohio and a life long shooter, hunter, and in later years an NRA certified firearms safety and shooting instructor and small caliber rifle bench competitor and coach, made sure that my brothers and I knew how to safely handle and effectively use them.
He started with explaining what each of his firearms were, what ammo they used, and how each one worked then took us along to the range with him to watch him and other people shoot and explained what he and they were doing.
When he thought we were ready he started us shooting with single shot 22 rifles and pistols and as we got bigger and more skilled introduced us to larger caliber firearms. To forget or fail to follow a rule resulted in a quick, and usually painful, reminder.
In 68 when I enlisted in the Marine Corps at 17 they were surprised and delighted with my firearms knowledge and shooting skills and refined them even further. My drill instructor would even use me as a training aid.

But does this mean that I think that there should be a law requiring training? No, but I do think it should be something pushed by responsible firearm owners, firearms sellers, and shooting ranges using peer pressure and incentives.
I also believe that training in firearms safety and shooting should be included in all schools taught in graduated stages as a voluntary extra curricular activity like football, baseball, and other sports.