My first 7" was something by (I think) The Clash. I bought it from Luton and Dunstable hospital fête because I liked the sleeve. However, I left it (and a football) with my shoes while I went on the bouncy castle. Afterwards, the record (and the football) were gone. My shoes were thankfully not stolen. I was probably about 7.
My first 12" single purchase was "OK Fred" by Errol Dunkley. I paid 20p at a Bring 'n Buy sale at my infant school. I was probably about 7.
It was some years before I could afford to buy my first brand new album which was "Strictly Business" by EPMD. I still listen to it pretty regulalrly. It's one of the best hip hop records of all time. I would've been 15 by then.
I had only really bought albums on tape before that. No idea what my first tape purchase was. Probably one of the earlier StreetSounds Electro comps when I was about 10 or 11?
I now have the vinyl version framed on the wall in my living room.
I don't think I bought a brand new CD until at least 2001. It was either Drukqs, or Wasted Sunday by Ovuca whichever came out first. I have since lost the Drukqs CD.
I was 28 by then.