I'm not the best person to be answering this because I'm relatively new to GODOT myself (though I have plenty of experience with other engines). I'm only answering because I'm not seeing anyone else answer.
For your first project, a complex ARPG is likely significantly overscoped for a single person. A senior developer could pull it off but I'd suggest other first projects. With godot 4 in its current state, I think a modern ARPG is iffy, depends on what kind of enemy counts, projectile counts, and effects you want. But its improving rapidly and by the time you've developed your skills to the point where you are ready for a project of that size, who knows.