Just deep understanding of the basics. The rest will come.

Particular attention to biochemistry, and immunology, and physiology.

For biochemistry my favourite book was lippincott for its incredible clarity.

Immunology was the Lange review of microbiology and immunology.

I consider anyone who hasn’t studied Guyton physiology thoroughly to not be learned in the discipline at all

all of these make the fundamentals so clear that it’ll carry you for the rest of your career. Makes everything easier