Keep the 2nd amendment and the laws as they currently stand.
I've gone back and forth on this for years. There have been times that I have thought some sort of mandatory training course, much like you need for a drivers license, would be a reasonable way to slow down the sale of guns into the hands of people who have no intentions of learning how to use them, storing them properly, or showing any other trait of being responsible owners.
But the reason that I have stepped away from that idea is that guns, at the most basic level, are a means of self-protection. It is a way to defend your home, your property, and most importantly the lives of yourself and your family. Who is the most in need of protection? Poor people who live in high crime areas. Who is the least likely to be able to afford or make time for a mandatory training course? Poor people who live in high crime areas. This is actually already demonstrated by the fact that ever since they removed Driver's Ed from high school curriculum, and began requiring people to pay the course fees themselves (up to $500), kids in low income neighborhoods are simply not getting their licenses anymore until they are much older. It's pretty hard to get to a job without a car, so this is just another road block for poor kids.
So while I feel like a mandatory course (like drivers ed) would reduce gun sales into the "wrong" hands, I also think it would reduce gun flow into the hands of those who actually need them. I think it would be pretty low of me to enjoy my own guns, which I'd have no problem acquiring because of my adequate free time and disposable income, while forcing others into an even more difficult situation.