The Op-Amp Foundation. Focus on Chapters 1 & 2. Master the ideal characteristics. Solve the 10 basic numerical problems on ( V_{out} ) calculation for inverting amps. Do not skip the "DC Imperfections" (Input bias current and offset voltage)—this is a favorite viva question.
The Math Phase. Dive into linear applications. Create a cheat sheet for every standard configuration: Summer, Subtractor, Integrator, Differentiator. Pay special attention to the Miller Integrator (with the resistor in parallel to the capacitor to prevent saturation). The Op-Amp Foundation
Happy engineering.