35 minutes ago, AidanD said:

error CS1525: Unexpected symbol `Vector3', expecting `class', `delegate', `enum', `interface', `partial', or `struct'

You’re missing the surrounding class :^)

using System;

public class ExampleComponent {
    public Vector3 ...

    public void Start() {
        // ...
    }
}

Learn Unity 3d . It is the simplest, and has  best tutorials for beginners.

For the latest Unity 5 tutorials you can refer to this https://unity3d.com/fr/learn/tutorials It contains very useful tips and tricks

If c++ is your language go with Unreal. Plus: great engine, it's hard to do something ugly with it. Cons: Assets on the store are not always cheap and tutorials might be harder to find in comparison with other engines. If you choose to go with c# unity is a great tool. Free, you'll find really good assets with a very affordable price, great tutorials but, if you really choose unity, go with c#, don't try to do on javascript. My first games were made in javascript and I had to rewrite the whole thing. and good luck!