Ok, Just two things to say..
1.
I would suggest, before you start upgrading things is to learn how your bike works, and how to maintain it. I’s sure the brakes grinding against the Tire (or rim…?) is not an issue that warrants an upgrade, you’re just going to have grinding noisy disc rubbing in the caliper then.
If the wheel alignment on your car is off.. getting new tires is not going to fix the issue.
2.
Getting a Lighter derailleur is VASTLY different from changing your handlebars just for the color.
Shaving weight is almost always a good thing (unless you go too far and sacrifice durability), but a lighter derailleur will also have a quicker, crisper, and.. lighter shifting action. Compare stamped metal derailleur to a carbon cage one and it’s going to seem like it’s flying across the cassette.
For now, I would suggest you invest your time and money in learning about your bike first. (like buy one of the bike maintenance manuals from Park Tools or Zinn). Any upgrades before then would just be a waste (a poorly installed and maintained set of disc brakes is not going to make any difference from a set of V-brakes)