Definitely start off with learning basic chemistry, followed by organic chemistry and then biochemistry if you want. I've made it up through my first year of o-chem with only having covered math up to trig/pre-calc and basic physics/biology. For me atleast, what order I went in depended a lot on what I was interested in at the time, so I found myself jumping around a ridiculous amount. Personally I started learning chemistry by stumbling through an o-chem book, before really getting down the fundamentals.What order you should learn, field wise, really depends a lot on your career path most of the time. For instance, if you're wanting to possibly end up working in the pharmaceutical development field (medicinal chemistry), it's more beneficial to major in organic chemistry, instead of medicinal/pharmaceutical chem. You can train an organic chemistry to be a good medicinal chemist, however someone with a 4year degree in medicinal chemistry will require a lot more work to become a competent organic chemist. Chemistry wise, look into getting an AP Chemistry study guide to learn from. "5 Steps to a 5" was a great guide for me. The books typically start off by covering basic chem and will cover everything you'd like in your college freshman chemistry class. Definitely take the AP Exam if you can, because you can get college credit for it. Just make sure to really do all the practice problems & tests that are included in the book, they help a lot. I got into organic chemistry next, which is really fun in my opinion; look around for torrents of "Organic Chemistry As a Second Language, by David Klein". There are two books, one for each semester of the class. They both double as workbooks too, so take advantage of that.The way I got started getting into neuroscience/pharmacology was really just by a spending a shit ton of time sitting at the computer reading through wikipedia, drug forums, and googling. I started learning what basic neurotransmitters there were, their functions, which drugs interacted with what receptors, what kind of effects/damages those drugs can cause to the brain, what subsequent psychological alterations those changes can cause, various psychological disorders and the neurological reasons behind them; what kind of things I could do to better my mind (like neurotroopics - seriously, if you dont already know, check out what benefits from taking stuff like magnesium supplements/nmda antagonists have); and harm reduction. I could go on for pages obviously, the general point was just that theres a vast amount of information you can easily learn from all those fields, and pretty efficiently.
