It all depends on preference and what you are hoping to achieve. Some things can be done in C++ that cannot be done in blueprint (but this is vary rare) and some things are easier to do in blueprints, especially with UI work and prototyping. You are also able to mix C++ with blueprints very well in Unreal once you get the hang of it.
The basics are macros called UPROPERTY() and UFUNCTION() in C++ that then expose properties and functions to your blueprints you create (inherited from your base C++ classes). I would recommend hitting the tutorials and looking at a mix of both, however if you are new to games development the blueprints are good and easier start.