There is a lot of info out there. Search this site, mkiv.com, supraforums.com (can't search, just browse), and clubna-t.com.
There isn't much difference in years.
Wikipedia will tell you the subtle differences in the years. Really buy whatever you can afford. Obviously, the newer and lower miles the better... unless you have a sexual attraction to OBD1 or something. btw Supras only come in TT and NA. Many many owners swap out the TTs for a single and can put up serious numbers.
These for example. Engines can easily push 1000+HP on stock internals and last for over 200k miles.
good luck to you