Every car in gt handles different so its hard to say what settings are right for one car type. But pretty much the first thing for maximum grip is to get racing suspension, racing soft, soft tyres, and racing mods.
For drift its just a matter of getting doing the follwing to ONLY the rear end:
- hard tyres
- soften up the spring rates
- lower the damper settings
- lowering the camber
- taking off any stabilisers or using soft ones
- lowering the downforce if you have race mods
of course its a bit of trial and error, but how else do you become an expert tuner?