Dragon 32, if I recall correctly.
Mostly try to learn some basic (probably was too young for that), play some games, and try to get the cassette to work. It almost certainly wasn't the right computer for a kid my age.
Later, if I recall correctly, some model of Atari ST, which again was mostly wasted, though it introduced me to graphics editing, and some 16MHz (with turbo on!) 286 computer with a 65MB hard drive and CGA graphics (later upgraded to EGA and eventually VGA, though that might have been with a later 486), which introduced me to DOS (and extended and expanded memory), WordStar, dBASE 3, Lotus123, LucasArts and Sierra adventures, Wing Commander, a multitude of CRPGs, and eventually Windows 3.x.
I didn't really get online until I went to the university, back in the glorious days of Yahoo, and the much superior Altavista, surfing on Netscape, before Internet Explorer ruined everything.
There were some great SGI Indigo machines (my first contact with a Unix type OS) and a prehistoric VAX machine with actual dumb terminals (never saw the actual server, sadly) for us to practice with there at the university, though, so that was great (though it didn't make up for the Pascal).
The turtle moves!