First was a Webley MK VI converted to .45 ACP. I was 13 and my mother had to buy the gun.
Second was a very nice Colt M-1917 .45 that was a Christmas gift when I was 16.
The first that I actually bought was either a S&W MK .II .455 or a Lend-Lease Colt .45 auto. I'm not sure which I bought first. I was 19 and stationed in Denver with the USAF. I shopped at Gart Bros and Dave Cook, and the clerks faked my age as 21 on the papers. Both said that they trusted me as a military policeman who might have to fight in Vietnam to own a pistol while under 21. I suspect that they wouldn't do that today. Times are different.
The Lend-Lease .45 had the usual British proof marks and was one of several with higher than usual fixed sights that were probably added by SOE or some other special operations force, I suspect. (Other .45 autos from the UK usually have normal sights.)
The first brand new commercial one was a Colt Gold Cup.45 auto with a special-ordered arched mainspring housing. I bought it in Newfoundland, via the BX store. I'd tell you how well it shot with Federal 230 grain Match grade ammo, but some would think that beyond my or the gun's capability. But it wasn't... I shot pretty well then.
If starting out in handguns today, I'd first buy a M-66-3 S&W .357 with four-inch barrel, and then a Model 60-7 snub .38. I think those are the best basic handguns, one for concealed use. Next, I'd add a stainless 5.5-inch bull-barreled Ruger .22 auto. If I was shooting a lot of full .357 ammo, I'd quickly add a Ruger GP-100. I love my GP, but as an all-round .357-capable gun that weighs less and is easier to conceal, the M-66 has an edge for most people.