For your first gun, something "throw away" but dependable wouldn't be a bad idea, i had a highpoint 9, less than 200 bucks, dumped thousands of rounds through it. It would give you a good idea of what size, and caliber suits you over allot of rounds and situations. When your done with it and...
My friend who is a leo said that in school they would often hear about reports where officers had emptied entire mags and thought they had fired only two or three shots, point being the ability to keep a round count in a firefight is slim at best.
I have the UTAS, hundreds of rounds and I'm still in love, 15 rounds of 3"mag without any pain, loading is great, chrome lined barrel looks like it did out of the box.
Choate mount, professionally installed, get a red dot and go as short as you like (legally). I have a choate on mine, nc star scope, zeroed about 600 rounds ago and its still there.
I just sold a rifle on consignment, i told the shop to ask what i had into it, he recommended a price much higher, it sold before i got home! Still about half gb price lol.