If you wanted to be expert in pharmacology, I recommended this reference :
1. Lippincott Illustrated Reviews: Pharmacology
2. pharmacotherapy a pathophysiologic approach 2017
They contain many core and simple concept of pharmacology, pathophysiology and also pharmacotherapy of disease. some guideline (algorithm) of disease that can be help. example if Hypertension the guideline is JNC or AHA. That can be very useful.
The most important thing is to concentrate on class effects, not individual drugs. It will be hard to memorize them drug by drug. Study the general class mechanism and effects, then move on to specific details on individual drugs if needed for the patient management part. Additionally, you can improve your understanding on drug effects by using different simulated pharmacology labs available online.
I think it is really important to be familiar with the class effects of drugs as an initial step, but to master pharmacology, specially for clinicians, it is very important also to know the specifications or individual variations between the drugs of the same class as well, not all drugs are the same. For example you can't prescribe Diclofenac as a NSAID for patient with heart disease but you can give him Naproxen, despite that both meds belong to the same class of medications but they are different and so on .....
from my point of view, pharmacology can be taken from two different ways:
if you are doing a postgraduate course in pharmacology, involved in a research or will be involved; its depends on your are of interest. pharmacology is a very wide discipline and to master an area of it, you need to have to a basic (sometimes advanced) knowledge in physiology, biology, biochemistry in general and pathophysiology of the disease you are interested in. you must familiarize yourself in how to put a hypothesis and propose an answer to that by applying different research methodologies and expecting an outcome.
however if you simply want to master it by memorizing drugs (clinical schools), start by looking at pharmacology deeply without studying any drugs. see the major receptor families, different transporters and their functions, enzymes action and most importantly different signalling pathways. you can find this in the first chapters of nearly all pharmacology books. then, you should familiarize yourself with major drug classes used in everyday practice. study (in general) their mechanism/s of action on different receptors/enzymes/transporters (or what ever the target is) and on different tissues (this is a critical point) and their side effects profile. after you have done this, go deeply into the different drugs within each class, see the differences of drugs within the same class in terms of efficacy, side effect profiles, DDI, CI...etc.
a very important point to consider is that mastering pharmacology dose not mean that the person will know the answer to any question on the spot! it is a huge area and probably mastering an area of pharmacology is more applicable .
what you can do instead is dig deeper into the areas you like to expand your knowledge in. i really advise you to use most updated edition of "Goodman & Gilman's The Pharmacological Basis of Therapeutics 13th Edition".