Oh man I can't remember it's over 30 years ago!
My mother, aunt and cousins owned several albums and 45s, not to mention numerous cassette tapes,
but I think my first self owned 45 somewehen in the early '80s, was
BMW's Buffalo Soldier 12" or
Pass the Dutchie by the underrated
Musical Youth, global number one!
I also can't remember what was my first bought lp either.
It was probably a
K-tel compilation with all the then current reggae hits.
Now I think about it, it's very odd; cause I can remember buying MJ's 'Thriller" in '83 possibly the first album I bought.
But I soon started to 'binge' on reggae releases so which one was first is lost in the foggy mists of yesteryear.

What I DO remember is buying in a secondhand comic-shop
Johnny Clarke's 'Rockers Time Now', Prince Far-I's 'Free from Sin' and
Greyhound's 'Mango Rock' (cool but underrated Reggae/Soul album, check it out) almost all at the same time! To this day favourite albums.
Nice times, nice topic.
Peace,
DJ