If you're dad has 3 bikes I'd assume he'd be a good source of information as well.....but here goes:
Black looks cool. Off the bike. On the bike no one will see how cool you look. In fact they just won't see you, so yes if you are going all black I'd recommend the reflective vest like you mentioned. As a new rider, you'll spend half your brain power just thinking about riding the bike when it should be 95% tasked towards clearing and watching traffic. You offset that crutch by being visible, at least until you get better.
Denim jeans are actually pretty sturdy, so if you had the kevlar enforced ones on your list I would make that my last priority.
Get gloves. Comfortable ones that would hold up if you took a dive.
All cheap helmet vs. a nice Shoei or Arai, etc. is very much a noticeable difference in noise, fit, weight, and comfort. If you plan on long rides at all I would absolutely suggest spending a little more on a nicer helmet.
Boots would be a good idea, or at least some sturdy shoes designed for riding.
Leather is nice, but it comes with a price tag that's not necessary. The textile jackets come in all kinds of colors and styles and it's pretty easy to find some that look awesome and are extremely safe. Definitely consider it to save some money and you might even like them better (like in the summer when it's fucking hot out).
I haven't driven my car since February, so I can attest to how much fun it is to ride and how cheap it is to maintain and gas up. However I'd be lying if I didn't say I haven't been scared a few times, so play it safe when you're transportation is inherently dangerous.
