You can buy older editions of textbooks for relatively low prices on amazon.
Before learning organic chemistry it is common to learn general chemistry. However, many organic chemistry texts provide you with a quick introduction to the principles of general chemistry required for reading their book. General chemistry helps in one's understanding of mechanisms, but one can still reason through organic chemistry without having a strong general chemistry background. However, once moving into a laboratory, the understanding of stoichiometry that is enforced throughout general chemistry becomes necessary to understand. Because of this, for any young buddying biochemist, a great place to start is general chemistry (which is very boring IMO compared to organic chemistry). While I was in college, Steven S. Zumdahl's Chemical Principles was the standard text.
After general chemistry, organic chemistry is a common next step. But, like I said before, you may be able to pick up an organic chemistry text while having no general chemistry background, and still adequately learn the material (especially if you use the internet to google concepts like electronegativity and orbitals which are often mentioned in organic chemistry). In terms of a book of choice, we used Janice Gorzynski Smith's Organic Chemistry. The progression of the text is beautiful and allows for great self learning. It does not breeze over any mechanisms and explains each step. It starts from the pure basics and slowly works its way up to real synthesis. After I finished that book I felt confident in the idea and principles of basic synthesis. However, it only emphasizes principles of mechanistic organic chemistry and does not teach one laboratory techniques.
Concurrently while studying from Smith's Organic Chemistry, we used Daniel R. Palleros's Experimental Organic Chemistry. This book does not do a great job at teaching mechanisms, but does a great job at teaching you the basic laboratory techniques that are employed in industry. Of course, as most do not have labs to practice in, I would purchase Smith's Organic Chemistry first, get the hang of that, and move forward from there. Regarding biochemistry and molecular biology. I believe the best introductory biochemistry book is Nelson and Cox's Lehninger Principles of Biochemistry. This book starts at a cellular level and moves deep into the realm of biochemistry. I find myself still referencing this book to this day. Though it is an introductory text, it encompasses a HUGE amount of biochemistry and is (once again IMO) the single most influential and informative book in the world of biochemistry. Many universities also use Voet and Voet's Biochemistry. I used this book as well and find it very useful, but it covers very little not covered in the previous and does not cover everything covered in the previous. Physical chemistry (quantum/thermo/stats analysis) is not necessary in the slightest way to understand the majority of academic journals being published in the American Journal of Biochemistry. Learning quantum is great fun, but really does not serve the organic chemist on a day to day, though it does help build an even stronger understanding of the materials at hand. If you are wishing to make a career in organic chemistry, it will be useful to know some physical chemistry principles. For such, Donald A. McQuarrie's Quantum Chemistry and Engel and Reid's Thermodynamics, Statistical Thermodynamics, & Kinetics are both great text.
In medical school we used Lieberman and Mark's Basic Medical Biochemistry A Clinical Approach, and Lieberman and Ricer's Biochemistry, Molecular Biology & Genetics. Both of these books are watered down biochemistry, appropriate for a physician, but inappropriate for the aspiring biochemist or organic chemist as they downplay mechanisms and stoichiometry and emphasize reactant/enzyme/product relations that are high yield on medical board exams.In medical school we also used Katsung, Masters, and Trevor's Basic and Clinical Pharmacology. This book is great. It has many of the drugs discussed here, a decent description of their mechanisms of action, their history, their cross talk with other medicine, and their side effects.
To understand actions downstream of the site of drug interaction, I recommend Guyton and Hall's Textbook of Medical Physiology. This is what I used throughout the first two years of medical school (though I still reference it to this day when I am feeling rusty). This book is the final step in building an understanding of what many of the drugs discussed here do downstream of their site of action. It has some advanced topics and is written in anticipation that the reader has a decent scientific background, but is a relatively easy read and with the help of google it should not be a challenge to read. During graduate school (was enrolled in a dual degree -MD/PhD - program, with the PhD offered from the molecular and cellular biology department), we actually used Nelson and Cox's Lehninger Principles of Biochemistry again. Of course, by that time most of the reading was from academic journals and no longer from textbooks, but I still was told to look in the book for certain concepts.
There is a forever vast body of knowledge regarding the subject of your interest, it goes both far and deep. You can't learn it all in a day. In fact, you can never learn it all, no one can. However, knowledge is power, and it's yours for the taking. I wish you the best of luck on your academic endeavors. I don't expect anyone to go out and buy every textbook I just listed. I just listed them to be of help, so you can see what level of background a professional in the field has, and so you have a reference of great text that may be useful in your future.
I wish you and all alike the best of luck in your pre/current biochemical endeavors, cheers!