Increasing chassis stiffness?

Hi. I would just to ask if what parts/braces are highly recommended to increase a car's chassis stiffness?

Car is a 2015 Honda City.

Added (1). * The Honda City that I'm talking about are the ones that are produced in Honda's Asian markets.

I can't wait till I can drive?

Man I'm just so pumped, I can drive in a year and its gonna be wicked sick! I know I sound like I'm 9 talking like this but I'm just so thrilled to the chance to get on the road and not have to ask my mom to drive me everywhere! I mean, my dad has been so chill about it, cause I've thought that I would get my buds honda but he was like "Well sure, your first car isn't gonna be a Ferrari or anything but I think we can get you something cooler than that." and then he went on telling me that he'll put a stipe and maybe a spoiler on it so it looks cool! Where he works he gets great deals on cars so thats a big plus and over all I'm just so pumped about it! I guess I gotta make this into a questions so nobody takes this down so uh, what can I do while I pass the time waiting and what should I prepare for the driving test?

What are some good first car options?

I still have approximately 3 years until I can start learning to drive, but I'm excited to drive so I'm looking at potential cars that could be good as first cars. I'm looking for something reliable yet sporty and fun (I'm a car enthusiast). My maximum price budget is $14,500 at most, which I think is quite reasonable and should result in me being able to drive a decent car. I've been thinking of either a 2015 Subaru WRX because by the time I'm able to get a car of my own, the 2015 model will be 5 years old and the Subaru's are very reliable and still fast af. My second choice would be a 2010 Mitsubishi Lancer because they can still look good once' they're modded, and the fuel efficiency seems to be pretty sustainable. My third choice would be a Lexus IS250 because they are sporty cars. I'm not very familiar with Lexus vehicles so I don't know if they have a good rep or not ect. I honestly would rather not have a Toyota or Honda because they seem basic and that isn't what I would like.

What would be a good mileage for a used car?

I'll be 16 soon and want to get my car as soon as possible… I'm looking at hondas from 2012-ish, what would be a good mileage? Is 50k a lot for the age? Would I want something with less mileage?