Thanks entropy.
I'll start by sharing my journey, then add what I hope will be helpful advice.
I am under 5'1", I have large palms although not long fingers, but not so much strength any more. I'm now in my 70's.
At age 67 I realized a firearm would be a good thing to own and know how to use. I grew up in a city and had never even shot a squirt gun. A class was offered that I felt comfortable going to, so I signed up. Although it was billed as a beginner introduction, only I and one other lady had never shot before. They first gave us "blue guns" to learn what a gun feels like and to drill into us the habit of not putting the finger in the trigger guard until ready to fire. Then it was time to shoot, a little voice was going "I'm not ready!" but I went up anyway since everyone else was. We proceeded to shoot a 22, a 38 revolver, then 9 mm, 40's and 45's. I did well with the 22, 38 and 45, the 9 and 40 were all over the place. I do not have any explanation for this. The main thing I got out of it was actually having fired.
Blabla, then I went to my local gun shop/range for a one-on-one lesson. From what I had learned by then I had already decided I wanted a revolver -- I am not mechanical and was terrified of having a gun I would have to take apart to clean.* The Ruger SP-101 I could not even complete the trigger pull on. The GP-100 fit my hand well. I wanted to try a Smith 686 Plus (because it has 7 shots). I didn't much like the grip it came with, largely due to the finger grooves, but it was nice to shoot, the trigger is very smooth. At a subsequent range visit they actually let me take both the GP-100 and the 686 Plus at the same time and I tested them alternately to avoid hand fatigue playing a role in my decision. I had decided on a 4" barrel because I had read it is more accurate and has less recoil. The Smith was way more accurate for me, so that's the one I selected. After I got it I put on a different grip (Hogue grooveless) that is more comfortable for me because it is fatter and my fingers are not constrained by the predefined grooves. At the time I lived in California where nobody gets a carry permit so the size wasn't a factor, but it is pretty big.
* A point about revolvers vs semi-auto that I did not know at the time but have since learned is that many semi-autos are very fussy about how they are held and may fail to fire just because of that, one thing I keep reading about is "limp-wristing".
Fast-forward to two years ago, I moved to Arizona which is consistently ranked the most gun-friendly state in the country. Here a person can carry concealed even without a permit. (A permit has advantages though, notably reciprocity with all the other states that give permits, and I now have one.) So I thought a small revolver would be ideal. In Cali I could never find a range that rented them, so I had never shot one. A friend in another state had an extra Model 36 he wanted to sell and I bought it from him. My range visit with it was extremely disappointing. I could not shoot it anywhere near as accurately as my 686 and it was also painful, with every shot the back of the teeny-tiny grip jammed into the soft tissue between my thumb and forefinger. Being that it's a somewhat collectible year and style, I kept it, but it just sits in my safe.
Shortly thereafter Colt came out with a new version of the King Cobra, which I was very interested to try because I read that the trigger was only 9 pounds, compared to about 12 pounds for a Smith. It comes with a 3" barrel and I believe also shoots .357 magnum although I only use .38 special. This fits my hand like it was made for me, shoots accurately, and is enough smaller than my 686 that I can carry it concealed, so that's what I now carry.
Moving right along, I now recently acquired an AR, in order to have something for home defense more powerful and with larger ammo capacity. I had one lesson and one range visit prior to COVID, and liked shooting it. With a lot of help from all the wonderful folks here on THR I learned how to take it apart, clean and lube it, put it back together, mount, zero, and use a sight. My first time doing those things took me three sessions of about two or three hours each because I was so freaked out, but now I can do it. It's very nice to shoot, no recoil to speak of. I still need to learn how to use a sling.
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The first piece of advice is try different guns and go with the one YOU shoot most accurately and most comfortably.
A couple of other things I've learned:
1. A revolver is good to learn to shoot on even if you decide you want a semi-auto. This is because the trigger is heavy and the pull is long, so you don't have a chance to get into bad shooting habits like flinching. A smooth trigger pull is very important. Practice dry-firing (using "snap caps" instead of real rounds) in your house. Put a dime on the end of the muzzle, when you "fire" the dime should not fall off.
2. Accuracy is the most important thing. Start at as close as 3 yards, when you can make a ragged hole, move back to 5 yards, and so forth. One thing that will help with accuracy is to maintain focus on the front sight even after you pull the trigger.
3. As soon as you are comfortable shooting with a two-handed grip, learn to shoot with only one hand. When you can do it with your strong-side hand, add your weak-side hand. If G-d forbid you are ever in a Situation, the bad guy may shoot you in one arm, but as long as you are alive you are still in the fight. Many people slightly cant the hand to shoot one-handed, I prefer standing sideways which I understand is really old-fashioned but that doesn't bother me. You will be pleasantly surprised to learn that shooting one-handed is not difficult if you learned to shoot two-handed without developing any bad habits.
4. Regarding not being able to rack the slide on a semi-auto, I think there is a way to do it that is not how men usually do it, I remember a lady who used to post here called Officer's Wife who described how her grandmother had taught her, I think it was similar to how I operate the charging handle on my AR -- I can't do it using my left hand with the gun mounted to my shoulder, but I can do it by bracing the butt against my midsection and using my right hand.
Now that I've used up way more than my share of pixels, I'll just close by saying you picked the best gun forum on the internet, everybody here is happy to help, so keep us posted on your progress and never hesitate to ask more questions.