Should be getting GT7 next week and that's exactly what I'll be looking forward to.
Back when I was a kid playing GT4 I was big into maxing every car I could, racing super softs etc., but since then I've been far more interested in doing things in a more interesting way.
I'd say they usually fall into these three categories:
OEM+ 'R' builds: minimal power increase but maximum rev limiter increase, slightly stiffer suspension, slightly lower ride height, slightly more aggressive toe angles, etc. (My favourite of these was a F430 I tuned in GT6)
Powerful cruiser/sleeper builds: saloons or GTs, minimum adjustment to the suspension etc. except maybe slight lowering or even softening the suspension further than stock, no transmission changes etc., but more powerful induction for effortless torque
Aggressive track-day builds: Low or mid-range turbo, short ratio gearbox, super intense/aggressive characteristics, almost always set up specifically for Tsukuba, so max rotation and acceleration