I think the first one I bought was Dire Straights, Money for nothin. However, I was given stuff I didn't want like that one with Billy Joel throwing a rock, and some all black ACDC album. My sis gave them to me so she could watch MTV one night.
I think the first record I bought with my own money, cant remember how old i was maybe 7 or 8: Genesis- Genesis Live: The Way We Walk Vol. 1 I was hooked on "I can't dance" when I was little.
Sesame Street Fever was my first record My first CD was Powerstation. I think my first cassette was Information Society
I also had plenty of Sesame Street, Electric Company, and Schoolhouse Rock LPs. I also had a bunch of book-and-45 combos, although the one I remember the most is a Superman vs. Mr. Mxyzptlk comic. (Yes, I had to Google the spelling of that.) First LPs that would be considered "music", purchased by my dad for my 8th birthday (on the last day of the 1970s) to go with the new record player: "(pronounced leh-nerd skin-nerd)" and "On the Road to Freedom" by Alvin Lee and Mylon LeFevre. First LP I bought on my own: Eagles, "The Long Run".
The first I bought with my own saved money was The Kinks - One For The Road. I had talked my parents into buying me others before that, and received albums as gifts.
First ever CD....Boomerang Soundtrack that i won from 104 KRBe back then....couldn't afford 21 bucks a CD and the only player i had was on my 486 Computer.
i'm not sure which came first, but these were the two: Houston Oilers #1 (7") Queen--Another One Bites the Dust (7")
Not counting kid stuff, the first I bought on my own was... Debbie Gibson. She wore a lot more clothes back then.