As said above.

My gold BBS RG-R's were 18x7.5 +48 F and 18x8.5 +50 R, but they had skinny tyres that they came with.
My white Work Meisters were 18x8 +35 F and 18x9 +45 R, with a 225/40/18 front and a 245/35/18 rear. You could easily fit a 255/35/18 rear in there, however both front and rear guards require guard rolling.

18x8 +35 was a bit of a hack to fit, so I suggest about an 18x8 +40F. The rear was a bit soft in comparison, so I recommend an 18x9 +40 rear - or there abouts - if you want a lowered, semi stanced daily driver capable S2K which offers very little inconvenience that width and offset are spot on IMO.