< Ancient language scholarship
I have some familiarity with Greek! Mostly Koine (the dialect of the Eastern Roman Empire from I think around 200 B.C. through the Byzantine period), although a little bit of Classical as well. I had two years of Classical Greek in college, then a few years ago got a textbook on Koine to re-familiarize myself with the language and specifically learn how Koine works. It's thankfully simpler than Classical.
The main thing I've noticed is that what vocabulary you need to learn depends on what you're going to be focusing on. So for me, I got into Koine to read early Christian texts (so the New Testament, early Christian writers, etc.), which means learning the vocabulary that those sources use and how they use it. Even then, some things are their own animal: the Greek of the Septuagint is almost its own dialect from a vocabulary standpoint.
Feel free to hit me up if you need any help with Greek!
My main interest is in the Byzantine era, so Koine it is for me :) Of course there are books for all kinds of periods, I found resources such as: Greek for Euclid, A reading course in Homeric Greek, and a lot of books for New Testament Greek, which is likely the best place to start for me.
Right now I am learning Greek vocabulary by proxy, that is, by learning the etymologies of the words I come across which have a greek origin, for example spagyria, "Originally coined by Paracelsus, the word comes from the Ancient Greek σπάω spao ('to separate, to draw out') and ἀγείρω ageiro ('to combine', 'to recombine', 'to gather')." (from Wikipedia)
Getting more and more into western esotericism and the like, I am ever more stimulated to start getting serious with Greek, but at the same time I have already my hands full, and I have neglected the Classical Chinese. It's hard being interested in everything under the sun.