For holsters, you're going to need to tell us more about how you will use it. You are likely to eventually find yourself with a large drawer full of holsters. For something such as a draw-from-concealment class, I would want a holster that was quick to draw from, with little in the way of retention, typically made from Kydex, and for which there are a huge number of makers out there. These holsters typically pinch in slightly at the trigger guard, providing the only retention they have. I have one from Uncle Mikes, this one:
http://holsters.unclemikes.com/Holsters ... ydex/54201
Someone probably introduced you to the Beretta 92. If they have been using it for awhile, they probably have several holsters, and if they're anything like me they have several similar holsters they like, only one of them they use. They might let one of the others go cheap.
If you are going to be out in bad weather, and your pistol is going to be one the outside of your clothes, you don't want leather.
For any other use, more retention might be a good idea. In general, some of the most dangerous things you will do with a pistol is holster it and draw it from a holster. Beware of the Serpa holster: some military units and some police agencies really like them, but many pistol schools ban them because of the frequency of people shooting themselves while drawing from them. Years ago I saw an advertisement for a police surplus Safariland holster with level III retention for less than $20 (there's a reason it was cheap), so I bought it, and found I could not get a pistol out of it without using both hands. Look at what other people use. Talk to Cops you know about what they use off Duty. I use thumb-break holsters a lot, especially the DeSantis leather pancake and a Bianchi. BerettaUSA has a number of offerings, some of which I have, or are similar to holsters I have from other makers:
https://www.berettausa.com/en-us/berett ... ies&mpp=24
For cleaning, I typically use a cleaner/lube/preservative, plus a toothbrush and a microfiber towel, most recently from these people:
https://www.superquickcleanguns.com
If you have something like severe Lead or Copper fouling, you'll need a rod and brushes, as well as aggressive solvents. The more aggressive they are, the more nasty the ingredients, so wear rubber gloves.
Shoot your pistol a lot before you do anything to it. Eventually, look at the single best improvement I have seen for the Beretta 92, the "Trigger Job In A Bag" from Langdon Tactical:
https://www.langdontactical.com/92-upgrade-kit/
The 92, as it comes from the factory has a Hammer/Mainspring that is 20+ pounds. Starting with a loaded, un-Cocked pistol, your first trigger pull will be enormously long and heavy because of that. Beretta uses that ridiculously heavy Hammer/Mainspring because some ammo somewhere has ridiculously hard primers. I have yet to find any ammo that needs a Hammer/Mainspring heavier than 16 pounds, and almost everything fires with just a 13 pound spring.
The coaches I have consulted say that you will learn to shoot better, faster using a .22 rimfire. They also tell me I will do better if I just have one trigger pull I work with, so I am using a .22 conversion kit on one of my Berettas. I shoot the 92 with conversion kit better than some of my match guns.
During the ammo shortage of 2008-2016, there was practically no .22 or 9mm to be found, but there was a good bit of .40 S&W. Converting a Beretta 92 to shoot .40 ammo requires a .40 barrel, slide and magazine.