The first episode I remember watching was TAR 2 in the Australian Outback, 9th leg I think, the one with the golf/mining detour. I don't know of I watched the original broadcasting of it (Back then I was about 7 years old, so I doubt it), but I'm pretty sure it was the first episode I watched.
I didn't watch TAR 3 through 7 for whatever reason, and then I saw the Family Edition commercials and thought that it would be interesting, so I decided to watch a couple episodes, and then lost interest.
I remember bits a piece of TAR 9 through 12, I specifically remember TAR 10 and 12 though, so I mist of watched those seasons quite a bit.
The first full season I watched was 13, and 14 got me hooked, one of my favourite seasons to date. I watched pretty much every episode since, with the exception of TAR 16 legs 7 through 10, that season was bad (I watched them later on YouTube). Now I'm going back and watching the seasons I missed, already got the first 6 down, on 7, and hoping to get 7 through 12 done by the end of the year.