I think a long time back I mentioned that my first Transformer was either Jazz or Skywarp, I can't remember which........but upon reflection thats not entirely true from a certain point of view.
My first "Transformer" was Gobot Pumper bought at K-Mart
My Dad didn't like the look of Transformers that day so I got a gobot.
What first got me into the franchise was my friends with cable more than anything else. I probably never saw most of the G1 episodes at first as with only three channels as a child finding the show wasn't always easy.(I did better on re-runs).
What I was into almost from the start was the comic, I remember getting issue #5(still my favorite cover to this day) at the local convienence store.
So in short I guess my friends introducing me to the concept was the starting point and from there I moved into the toys and comics and then later the cartoon.