the first question would be how low are you/planning to be?

this will determine what size rims you can fit on without rolling and using the factory spec camber

if you are going to roll the guards then the shop doing it for you (if thats where you're getting it done) will also trim your inner guards because "apparently" its a need before rolling can commence.

im currently running a 18x8 +55 front and 18x9 +65 (with a 25mm spacer, making it a +40 realliy...) the fronts are tucked, a bit sunken (due to offset) not rolled and guards have not been trimmed. the rears however have been rolled/guards fully removed and they are tucking as well, the rears are set to factory spec (-1), but the fronts have a bit more negative camber than factory because i dont have adjustable camber arms yet

but with my amount of drop, the 245/40's i had on it were rubbing on the rear bar quite alot (so much actually the screw holding the rear bar in broke free and went straight into my tyre ==" maybe because i had 3 other people in the car too but it still scrubbed every now and then by myself especially duing cornering) so i had to get a pair of 225/40s so that it would hopefully clear with passengers

i personally wouldnt go any wider but maybe a bit lower offset for front and rear, the fronts are just sunk a little bit, the rears arent exactly flush but a lower offset should bring it out a bit. but once again it all comes down to how low your car is/will be

hope this helps you and sorry for the essay =P