My first "Synth" was a Casio MT-68 (and by "Synth", I mean totally electronic keyboard). I'd wanted a Realistic Concertmate MG-1 and a Korg MS-20 for about 3-4 years beforehand, but my parents' budget couldn't stretch to either... (I still remember the Tandy / Radio Shack catalogue ad for the MG-1 - it had a primitive cartoon / pencil line drawing of an "Artiste" who looked not unlike Elton John, playing a generic keyboard, and some spiel about "That Moog Sound"
The first actual "Synth" I owned (and by "Synth" I mean a totally electronic keyboard that I could make my own sounds with), was a Korg Poly 800 - I bought it with an unemployment benefit check (from a store in Romford, Essex, UK), after months of saving. I went to the store to buy a Yamaha DX100 (for £100), that I'd reserved by phone, and they'd sold it to someone else by the time I got there... However, they had a GOOD salesman, and he persuaded me to spend my hard earned welfare on the Poly 800 for £5 less... And it rocked.
Topically, I just bought my third for $50, and finally did the filter mod. And it now does things that I never realised were possible, 13 years ago..!
Always knew there was something cool about the Poly 800..!
BTW - back when I first lusted after an MG-1, my hero was Bruno on "Fame" - and I couldn't even PLAY keyboards then...