Growing up my father was the gun collector, so I really never saw the need to buy my own. Anytime we went hunting or to the range he would let me take my pick. At the time, being young, I thought my dad owned every gun ever made because no matter what I needed, he had it.
I would say about 10 years or so ago for Christmas he gave me a Ruger Single Six with the .22mag conversion cylinder. And then suddenly a lightbulb seemed to go off with me thinking "Wait a minute...I can actually own these myself now...I dont need to just go to the old mans safe?!" Which started me on a path of newbie moronic purchases. I grabbed a bubba'd SKS off armslist, sold it because it sucked, bought a Llama compact 1911, sold it because it just kinda left me "meh", bought a Ruger P85 in a private sale. The P85 was a beast, but was big and wanted to move to something more "carry friendly", and at this point was starting to get my head firmly on my shoulders about whats what in the firearms world. So I sold it for what I paid for it, added a bit to the amount and bought a Glock 19 gen 3 from Colfax Guns and Ammo. It became my carry piece for a number of years. Still have it and shoot it probably the best out of my "carry guns".
Somewhere in there I went through the Mosin stage...where I bought one for $90 bucks from a gun show. Bought and sold a few over the years.
Anyway...if I had to peg any of my guns as my real "first" I would count my Glock 19 because I feel, looking back, it was the first one I bought when I really knew what I was doing other than just grabbing whatever I could for whatever money I happened to have.