This is a huge topic and involves deeply personal opinions. However I do want to put out what I have learned in years of buying gear and trying it out. Of course, the conditions in which you use or expect to use your gear make for a huge difference in what gear is good for you. But there is still some stuff that is always good to have and some that is worth avoiding at all costs. A good pistol holster, go-bag, magazine pouches, tactical/combat/police belt and even load bearing vest, are needed or useful to just about anyone interested in the guns talked about on this site.
Competitions are great, but I have no plans abandon realistic gear to win one. I would rather come last and use the opportunity to get better at practical shooting. Guns have many uses, but mine are primarily for killing people. I will not draw a gun with no intent to use it - for me, I carry them to deliver lead where I want it, not to intimidate people. Chasing increased speed and function from gear is what has driven me to spend countless hours online looking at every bit of gear I ever heard about. There is a whole lot out there and I can't test it all. But with as many buddies and co-workers as I have that all have the money and interest to try new things, I have been able to see and test a lot of gear. I don't feel that less is more when it comes to ammo. While it may be true that statistically most shootings only need 2 rounds to be decided once way or another, it is also true that statistically most people never need a gun to defend themselves. I don't carry for the most likely, I carry to be as prepared as possible for the unlikely. So I carry 1-4 spare pistol magazines at a minimum.
I carry at least one gun at all times for work, so gear needs to be comfortable. I have a 34” waist and my belt is premium real estate for battle equipment. I prioritize pistol ammo on my left side, on the logic that needing to reload a pistol in a firefight is a more time sensitive priority than anything else. Behind the pistol mags, I have 2 rifle mags and I want at least one of them to be very, very easy to get to.