One thing to consider if the trigger system. Many years ago I started when you had only two basic choices. One being a revolver and the other being a single action auto. Since them I think I have tried just about everything except a HK P7 squeeze cocker. Try some different guns but since I like the same trigger pull on every shot, I have sold off everything that has a different trigger pull between the first and second shots. I have kept,
Colt single action autos
Beretta double action only
revolvers (SW's and Taurus's)
Glocks
one exception...CZ75 because it can be carried cocked and locked like a 1911.
I found that, for me, the transition between the long heavy first pull and the light second pull of a SA/DA gun like a Beretta 92f or a SW 5906 was too difficult for me to master. It may not be for others but it was for me.
I suggest you start off learning properly and I highly recommend the Glock. It does not have a external safety but neither does any revolver I own nor any DA only auto. It is virtually indestructible, all parts are readily available, none require fitting by a gunsmith, good factory magazines are inexpensive and readily available, holsters and accessories are also inexpensive and available also. Many will disagree, but I plan to start my son on a Glock 19, as a carry gun, when he turns 21. Also, as you stated, 9mm ammo is the least expensive so the 19/17 is going to be your best bet. Also, since you can't really hurt a Glock or wear one out, I would say find a like new in box used one for around $425, which is a common used price, and use the rest of the money for holsters, training and ammo.