My Advice,
Don’t think about “Start From Scratch”. It makes no sense to use a game engine and then try to start from scratch. You can’t start from scratch making a video game, everything depends on libraries already written.
Just use the system as it’s given when you are starting out with it. If you don’t like the framework that’s given, use another game engine that your more comfortable. It’s very flexible, so I can’t think of a game-type that you couldn’t make with it.
Start with a project template and see how it’s put together before starting with a blank project. Such as top-down shooter.