You're going to have to ask someone running a 15x8 about those specifics. 0 or -10 might work but you might have to run narrow tires so they don't rub. You need to see what tire sizes are available in 15, 16 and 17" before getting rims. It's getting harder to find the correct size tires for 15" wheels. I run 225/45-15 tires on my race car and have to roll the wheel lips.
You might mind getting flares. There's the cost of the flares and the installation. The wheel wells have to be cut and the rear inner fenders need to be welded and sealed to the quarters. To properly fill out the flares you'll want 8 or 9" wide rims and really wide tires. That adds to the budget.
The rubbing I had on my street Z was with the inner lip of the 15x7 wheel against the caliper. Depending on the tires and wheels you get you could have rub with the caliper/wheel, strut/tire and fender lip/tire.
What are you looking for with tires and rims? The widest that fit under the fenders? Widest that fit with flares? Wide wheels and stretched tires?
Chuck