My first 45 (I was 12 at the time) was "Upside Down" with Diana Ross (it had just come out; yes I'm that old). My first LP was Supertramp's "Crime of the Century".
Holy crap! That was my first 45!
First album, I believe, was "Music Machine" from K-Tel ('cause it had a cool robot on the front).
First real album would have been Eagles - The Long Run.
Yes, I realise that the 45 came out after the albums - I like to start big!