I know I promised a 3-gun gear and guns article, but I think what most people (myself included) need more is to fix themselves.
I've shed more bad habits just this year than I even knew I had. Competition is a really great way to gage your skills and show you where your weak spots are. Had I not joined USPSA and competed regularly, I would not know I had a faulty targeting program, my reloads were too slow, and I didn't know the first thing about prioritizing targets and making a stage plan (which I now think would help prioritize targets in real life combat). I have a lot of stuff to work on during the off season (Iowa is cold, and my days of being cold, tired, and hungry are long past). People who get testy at the suggestion of competition are probably afraid of finding out just how incomplete their skill sets are. So what follows is a short list of stuff I'm bad at, and quick ways to make up a second here and there.
Your posture makes a difference. The "tactical turtle" is not a great choice if you take it too far. I have been working on keeping my head up since I saw a Jerry Miculek video where he explicitly says not to do the turtle. I'll be darned if my scores haven't climbed wildly since then. I still reflexively raise my shoulders a little, but I'm no longer tucking my jaw down like I did only a month or two ago. Why is this a big deal? Imagine hanging a picture on your wall. Do you tuck your head down and pull in your jaw to eyeball it level? No. You hold your head up squarely over your shoulders and look straight at it. The same is true of your sights. If your head is tucked in and down, you aren't looking straight and level at your sights. It may not make a difference at seven yards, but from 25 and 50 it will make a world of difference. Here's a video of me not turtling at all:
Now me turtling slightly, but head still up-ish:
Drawing can shave time off your score too. Time to first shot is a big deal, so I practice drawing and dry-firing a lot. I know it's a pain, but put your holster on, grab your handgun and a snapcap and go to town. Equally, you could do this with your rifle or shotgun and a snap cap. I do that once in a while, but not super often. It's free and it's easy.
Again, put your gear on and grab your EMPTY magazines and put a snap cap in there (NOT LIVE AMMO, DAMMIT) and practice your reloads. From empty (emergency reload), on the move, topping off, etc. USPSA and 3GN allow you to top the gun off and drop partial mags on the ground. IDPA does not. If you're practicing for your specific discipline, make sure you're adhering to the rules. Here's a reasonably quick reload:
(Hit factor 9.725, thank you)
Most of the 3-gun matches in my neck of the woods are on fairly short ranges. Typically less than 100 yards. So what would help a lot is to be able to make good offhand hits from say, 50-100 yards. One really good way to get good offhand is to buy an air rifle and set up a 10 meter range and shoot at absurdly small targets. I set up such a range in my basement and shoot at printer paper with a ~6mm target (2MOA at 10 meters) using an old GAMO piston-powered rifle and a really bad 4x scope. I got my 6mm dot in two shots the other night:
As for the shotgun, well get snap caps and put your belt on and practice your reload. Practice until you get blisters and your fingernails bleed. Then practice some more. Dry your tears and practice more after that. Then get your stuff back out and practice your reloads some more. If you have trouble making your hits, well, I suppose busting some clays would help. Otherwise, it's the reload that will move your name up the list. Unfortunately, the only remedy is practice.
And that's really the one thing you should take away from this whole piece. Just practice. Dry practice is worth way more than you think, and it's cheap if not free. Shut your X-Station360 or PlayBox4 off and pick up your gear. Just 20-30 minutes a day does wonders.
Oh yeah, and all the stuff you need to practice will pay off in real combat also.