Happy to hear you bought a kit! And welcome!
If you go 15´s i have tested it a bit. Ive got 15x9" et0 with 38mm spacers in the rear. Fits like a glove. In front ive got 15x8" et0 no spacer, but there i did get a bit rubbing. So i had to widen wheelarches about 1". So if i had bought 10-20et they would have been just fine. Maybe this helps a bit.
One more important thing is how much stretch you have on the tyres, i got a small amount of stretch as i have 225/45-15 in rear and 195/50-15 up in front, so that saves me a bit too
Best regards Andreas