Some Ivy league universities, and other major public universities, have opened some of their online courses to non-students. Sort of like auditing a class but less official.

The upside is it's free, you only have to pay for the books, and you get a structure to participate in.

The downside is since it's free, lots of people sign up then never do the work.

What I generally do is start with Wikipedia on a subject that I'm interested in but don't have a lot of knowledge on, and I make a note of what information un the article grabs my attention. Then I look at the attribution to see what book it came from and then look it up to see if it's interesting. Then purchase and read!

1. Start by reading any book/article/blog that sounds like it's interesting to you. Don't worry about topics, or gaining a deep understanding of the book, or anything like that, just read stuff that interests you. Personally, I would focus more on reading books then on webpages. If you do read webpages, make sure you always read their bibliography and follow up on their sources. If you can get access, online Journals are also excellent. Podcasts I don't find very good, and they're difficult to reference later on.

2. As you read all of these books, ask yourself what about it you find so interesting. Specifically, in the books you read, you will find some chapters that fascinate you, and some you find so boring you could cry. Focus on what exactly you find so interesting about your favorite chapters. If you're anything like me, you will come to find out that what you thought was an unfocussed interest in a wide variety of topics, is actually something that is very focused. For example, you mentioned a bunch of different cultures that you were interested in, but maybe what you're really interested in is how consumer goods effect culture. For example, how did the discovery and cultivation of tea influence the chinese? One important note here is don't get to bogged down in chapters that don't interest you. Feel free to skim the book when you first get it, and make sure to read all of the chapters that interest you most. You can go back to the others later if you want. I've made the mistake of dropping books because I hit I a chapter I didn't like, only to find out that other chapters were more interesting to me

3. At this point you've narrowed your interests considerably, but here's where things get difficult. Your interest is still somewhat broad (while chinese and tea is just one item, and the chinese are just one civilization, there are lots of other goods and cultures out there), and your knowledge is still rather vague and unstructured; you've read books, but you haven't brought your thoughts together in a cohesive manner. At this point, you rely on dumb luck and and that annoying question every 2 years asks constantly; why? The dumb luck means that you should focus on learning more about the things you only know a little bit about. Your interest was peaked by chinese and tea by luck, but keep going with that. Keep asking yourself who cultivated tea, why did they do it, how did they do it, when and why did certain advancements in tea growing and distribution come about, how did politics effect the distribution of tea, how did tea effect china's relations with other countries, why, why, why, and more why. Writing down specific questions that you have and where you found the answers is a huge help.

Don't be afraid to read about other commodities and other civilizations, but keep bringing everything back to that very narrow, core topic. What you're starting to do is develop rigor. You now know a lot about this field, and in knowing so much about this topic, it leads quite naturally to other topics of interest. Now instead of just tea, you're looking at silk, salt, and jade both in china and in countries around china. You're starting to look at how these goods effected china's relationship with other countries, and how goods like tea and silk caused huge problems between china and the british empire.

4. You know a lot about your topic, and a bunch about related topics, now you branch out more and more. You've learned how to learn about one topic, now use that to learn about other things you might be interested in.

My own journey went a little bit like this. I realized that there was a huge hole in my knowledge of history. I know almost nothing about world history between Columbus's discovery of America and the American declaration of indepence (I'm American, go figure). I started looking for any book or website that was from this time period, was not about American history, and looked interesting to me. I found myself more and more coming back to military advancements during that time period. Before columbus, there were very few guns, and only a few cannons in battles. Fast forward to the American revolution, and suddenly no one wears armor anymore, everyone uses guns, and they all stand in lines to shoot at each other. How the hell did that happen?

The first book I found was William Guthrie's "Battles of the Thirty Years war: from White mountain to Nordlingen." It was a somewhat technical book but it hooked me, and gave me an in to other books. I started reading more about the 30 years war. I didn't have any particular interest in that war specifically, but it was where I started, and there was a lot of interesting stuff there. Gradually my interests expanded to the early modern period of warfare, from 1500-1700. But what I found more and more was that I was interested in how and why warfare changed in that time period. Eventually I found my true interest; the evolution of logistics that allowed the creation and maintenance of standing armies in Europe. My time period has expanded to include the 18th century, but I still go back to the 17th century and the 30 year's war from time to time. It was my first love after all.

In addition to books and online resources I've found podcasts, select-tv programs, museums and even some video games (assassins creed series) to be fun alternative methods for history learning. Or... If you have the time and money I'd suggest personally visiting some of the areas you are interested in.