Beginner Help

Hello, I know there is a lot of material on this forum, but I just want to make sure I get the right things. My idea is to get an Ardusimple board, which I understand comes with a GPS antenna already. I want to achieve 20cm accuracy, at least that’s my goal right now. So, I need an Ardusimple board, some kind of Windows tablet like a Panasonic FZ G1, but that’s a bit expensive, and some kind of wheel sensors that measure the angle the wheels are at—I think that’s what I need—and some kind of motor that I will attach some soft piece to steer the steering wheel. Additionally, I think I need some sort of gyro sensor to help with steering accuracy. I’m not sure if I need those, but I feel like the accuracy won’t be good without them. I’m sorry, I am very new to this, so could anyone please give me links to the correct boards and things I should get? Also, is the 20cm accuracy free? I am in Estonia so I’d like to make sure I don’t need some basestation or thing up to get 20cm accuracy. Isn’t it just free?

Edit:
i just realized i need some kind of arduino board for the sensors also and im scared a bit that the price is going to add up so if someone could please give me a general price range of what it will be? i want it to be under 1,000eur.

Go through each item in the table of contents. It lays out what you will need and some recommendations on where to get it.