… expanding on the good advice already given:
Ninja 500 vs GSXR: The GSXR is a race bike, not appropriate for someone starting out. The Ninja is an great starter that you won’t soon outgrow. Also, it’s been virtually unchanged since the Civil War or something, so parts are cheap and readily available.
Helmets: Endless debate, but according to tests and research (including the Hurt Report), any properly fitting DOT approved full-face helmet will protect your head from impacts that are low enough not to kill you regardless of the helmet. In other words, in the Hurt crash study, by the time any helmet failed, the rider’s body had already been so damaged that they would have died regardless of head injuries. My advice, pay what it takes to get the fit and features you need and that will keep you from being distracted. Beyond that, the safest helmet is probably the orange one.
Insurance: Your quote probably includes medical liability (for the other guy), but may not include you or a passenger. It’s not too expensive to add some basic coverage, but note that there are per-person and per-accident limits and $15K coverage won’t last long in a hospital.