I learned mostly by watching YouTube...Educated Barfly, Anders, Kevin Kos, etc. I found that only took me so far, so starting buying books that I found interesting. I don't watch the YouTube videos nearly as much, as I found most of the main personalities have moved on to ingredients that are fairly obscure that I rarely have, or that includes ingredients that take a science lab to create, (don't get me wrong, I love the chemistry side of mixology and do what I can with what I have) and I don't feel the average person ever really has in their home bar. It's now mostly experimentation. There are really only a few different "formulas" for cocktails, so I'll pretty much try different ingredients with the standard ratios...then adjust as necessary to my taste. I don't find it too expensive as I'm not making more than about 4-5 drinks a week, if that.