Actually, I don't have a recommendation, unfortunately. There are many different fields in biology, and learning each one can be a few years of work, plus the common foundations - so the question isn't how do you learn but "How much do you need to know to do a specific job?"

Unfortunately, biology is the opposite of programming. Programming is a logical set of tools that build on each other. If you learn arrays, or dictionaries or data structures, you can go out and apply them logically. You can figure out which one will have the best performance in a given situation, and optimization is a logical extension of what you know. You can spend a life time learning, but the basics don't change.

In biology, EVERYTHING is an exception to something else. Learn the entire "biochemical pathway" chart, and then you'll discover than some animals do things differently, or short circuit pieces of it, or just get a specific chemical from their diet and don't need to do a certain part of it. It's all chaos. Biology is the mad hatter's perspective and there's no real guarantee that something is going to work the way you think it should, or the way you were taught. eg. Translation of RNA to protein always begins with a Methionine (AUG codon)... except that sometimes it doesn't. Sometime organisms have found a way to get things started with a missing base, or sometime just that things are wobbly.. or maybe sometimes it's just not at all what you think it's going to be.

That's the rambly way of saying that you'll never know what you need to know until it's too late and you discover something was wrong. For my Masters thesis, I worked on a really slow growing bacteria, and was trying to convince it to do something for months (take up a plasmid so I could knock out a gene). I worked on that system for about a year, and never got it to work. A couple years later, working on a different project, I discovered that the post-doc who set up the system had missed a critical detail: the half life of one of the antibiotics, to which the entire system had been build around, was shorter than the incubation time of the bacteria we were growing. The system could never have worked on that organism, and no amount of work would ever have changed it. I wasted months on that, and never once thought to validate the actual system that had been used by the guy for a year before I started. Who knows what to make of the data he'd recorded.... is it all garbage? I really don't know.

How deep would I have to have studied to know to look at the half life of Kanemycin? I haven't a clue. In biology, it's not what you know that gets you - it's what you don't know.