Dude forget looking at GT's from the late nineties/early 00's nowhere near the brand they were bitd (very recent ones are ok)
Forget most brands from bitd
If your looking on ebay for summat to get back into riding have a look for a new school bike
Brands like
Fit
Wethepeople
Verde
Sunday
Subrosa
Colony
Have a look at rad shop, theres loads to choose from
Decide what you want to spend, how tall are you? theres top tubes in differant lengths
What sort of riding, race or freestyle?