with 235's, i was spinning them up everywhere, then with my 31"s, it was just right with stock gears. i think its another one of those suzuki mysteries, where suzuki had a grand plan where they designed the vitaras to run 31"s. hehehe
anyway, i have 33"s, and i can still hold about 120km/h on the highway/freeway. thats about 75mp/h.
but going off road is a different story. i can live with going a bit slower on the free way, but going too fast off road doesnt seem to tickle my fancy so much.
31"s are a good size for stock, and you soon learn to live happily with them. then you can slowly save for some crawler gears, or R&Ps, but i dont think its absolutely necessary.
i dont do a lot of rock driving or anything like that, its mostly mud where i am, so wheel speed is the key.
lift doesnt really influence your gearing, but more so how much clearance you can have for tyres, and a BL sorta sorts that out. obviously, a lifted or higher COG will also require a change of driving style in most cases.