Sorry for the slow reply, I was gone over the weekend.
I'm a big fan of doing exactly what you said! Make sure things are right on the Z (or make them right) before you start doing anything else.
I just dropped some major coin on my brakes and should be getting some new tires any day now.
After making sure that everything works like it should, if it's me (and depending on your budget), I'd start with suspension stuff. The Z has no way to adjust the front camber and only camber bolts in the rear. For being a sports car Nissan didn't make the stock suspension very adjustable. I'd take care of all of that before you get lowered (if you're looking for that) since you'll need to do it once you do and most owners aren't prepared for the additional expense.