Since you are throwing out lots of issues, I will throw out a few things to think about.
Lots of powders will work. I load for 9 different rifle calibers. There are a few that work better for some rounds and if I am tailoring loads I hunt for those powders. That said, there are some powders that work for just about everything. And then today, there is what you can find. As 5 run said, you want different powders for different bullet weights if you want to create the best load.
In the 223/556 I load for a single shot, a bolt action, a Mini 14 and some ARs. Your barrel length and twist will decide what shoots well and what scatters. My 1/9 twist will shoot most bullets well enough for me with 55 grain bullets in the AR and Mini 14. It is easy to find H335 and IMR 3031. I use more 3031 than anything else because I use it for 30-30, 243, 308, 30-06 and 300 WBY with the lighter bullets. For the bolt gun I load 34 and 40 grain bullets and it love the 3031.
I do not load the 65 grain and heavier bullets for the AR, the heavy bullets do not do well in my 16 inch barrel. I do shoot the 75 grain Wolf hollow point in it, and they are my self defense load, but they are not that accurate so I do not load them. Also, the heavy bullets lose a lot of velocity in the short barrels, with most powders. So, if you shoot the heavy bullets also, you really need two powders. I say that assuming you are wanting to maximize velocity. If you are just wanting to shoot targets at 100 yards, then most any powder will do and just ignore that comment.
The chart below shows why different powders do much better with the heavy bullets. About 200 fps more and less pressure.
For my AR and Mini, I load only 50 and 55 grain bullets, they are perfect for my guns. The 24 inch barrel bolt gun is a totally different animal. You do not use the same powders. If you can find it, I might suggest the 223 CFE, it gives much better velocity and is a cleaner powder, a big deal in ARs.
Below is a chart from the Hodgen site showing recommended powders. Note that Varget and H4895 are superior for the heavy bullets. Also, the beauty of this Hodgen data is that it is from a 15 inch barrel, so if you shoot a standard 16 inch carbine, it is spot on. Reloading manuals are for safety not precision. For example, the Nosler manual uses a 24 inch barrel for all loads with bullets from 40-69 grains. All the long range loads, 70-80 grain bullets are tested in a 20 inch barrel. My 2 Speer manuals both used a Mini 14 for their data with all bullets. My IMR is different, as is my Winchester manual and my Lee manual does not even give barrel lengths.
You need a manual for safety and to learn the process. It is wise to find someone who has reloaded for a few years to get you started. As far as basic guidance, the Lee Manual is about as good as it gets. He goes into a lot of detail and includes how to develop reduced loads and things like that. I just bought the Nosler manual, my latest, unless you shoot long range rifle, I do not recommend it. It is lousy on handgun data.
One last thought. If you are reloading for an AR. Most AR cut for 223 have very tight chambers designed for accuracy. There are two types/sizes of reloading seating dies. On paper they are both for the same case, but the small base sizing die squeezes the case down a tiny bit more., I think .003. If you are shooting hot ammo or 5.56 ammo sometimes the brass needs a little more resizing for the 223 chamber. The high end guns are more likely to have the tight chamber. When you reload brass for the AR, you must trim every case and resize every case, there is not much tolerance. If you have a tight chamber, they stop sooner when dirty because they do not have much room for carbon buildup.
Ordinarily I buy the cheap Lee dies but in the case of reloading for an AR, I suggest you small base sizing die. If you have a tight chamber you will need one anyway. I have corrected that issue for many folks new to ARs, including myself, my first AR had a tight chamber. I would fire about 40 rounds of factory ammo and it would start to jam. The chamber just had no room to accept much blow by. An AR needs a proper case, a shiny chamber and a wet BCG and chamber to run a long time without cleaning.
Reloading Data Center | Hodgdon (hodgdonreloading.com)
Anyway just some thoughts before you buy a bunch of reloading stuff. I learned the hard way.