Medical training would probably be the most useful, as injuries are far more common than gunfights.
As far as firearms stuff, being TFL and all...
For anything, make sure you understand how the law applies in your area and your situation. If you don't know what you can legally do, the chances of winding up in hot water after an incident skyrocket.
Get GOOD with your carry piece. Basically, you must know how good a shot you can make under stress, and how quick you can do it. It's not easy to be capable and know your limits. It takes a lot of practice and work. The last thing any of us want is to engage a criminal with that kind of force and not succeed! If you are in first responder mode, it might not just be your safety in the balance.
Depending on your role, the advice for pistol holds the same. Don't think that a hundred rounds a year will make you a great marksman.
If your job might see you doing things like searches, you'll want to study up on things like room clearing in various iterations (1-man, 2-man, and team), use of lights, differences between real cover and concealment, various tips and tricks to turn a shot into a safe one rather than putting innocents at risk, etc.
Hand to Hand:
Whatever firearm you carry should not be your only tool. If you think you might get into conflict, you need to be able to negotiate the full spectrum from words to lethal force with or without the tools you normally carry.
Obviously, that is a LOT to learn, so start with the basics, and get darn good at those first. You need to know when and how to use your skills, so basic skills and legal stuff should come first. The rest will follow, in time, if you keep at it.