I'm not a super expert or a lawyer but I'd add these suggestions(keeping $ & time as factors);
Join the NRA, www.nra.org
. They support legal & 2A issues and provide training resources.
Learn & understand the gun laws/use of force laws in your area. Be aware of what you can & can't do or what you can lawfully carry. See www.gunlawguide.com www.usa.gov www.atf.gov www.handgunlaw.us
. Atty David Wong wrote a useful legal guide to gun/knife laws for private citizens too. NOTE; some laws or state regulations change too, check often for any changes.
Get good training guides/DVDs, www.gunvideo.com www.paladin-press.com
. Take classes or seminars with top instructors or well known programs. Massad Ayoob, John Shaw(Mid-South), Clint Smith, Duane Dieter, Jeff Gonzales are highly respected. SIG-Sauer & Smith and Wesson also have classes-top programs.
A lot of "experts" have sprung up in the last 10 years across the USA claiming to be the "best" for skill training/tactics. Learn more about an instructor or class before you drop a lot of $. You can also take a 4hr workshop or 1 day class to judge the program's merits. Some firearm/tactics instructors are better than others.
Finally, stay fit & follow a healthy lifestyle. I know it's not easy & there are many ways to eat junk food or slack off but if you are in decent shape it may help you in a critical event or even avoid a problem.
Thugs & crooks look for low threat, "easy" targets. You'll also look & sound more credible if you later become a instructor/homeland security official if you are in shape. Sad, but true; people judge you by your appearance in today's world.