For game logic, it's recommended to use GDScript over GDNative since it has much better usability
Depends on particular game structure actually.
For instance, I came to Godot from another (rendering) engine and most of my logic (AI, game entities, relations) were already written in C++, so there's no point for me to reimplement this in GDScript.
But yes, as introductory step I'd also recommend (at least to be familiar with) GDScript.
Although my projects are mostly C++, I use GDScript too, for prototyping, configs, debug.
C++ is more capable as a language, but it requires additional setup (sometimes not very obvious for newcomer) where GDScript is ready to use from the start.