Two Months of Greek
As I mentioned, I'm studying ancient Greek. Most of the vocabulary my textbook has been giving me so far consists of farm animals, so the exercises I'm working on right now are translating silly things like, "we sleep all the time because we are cats," or "he has horses because he is a farmer," or "the pigs are chasing the farmer."
I figure that makes sense, though, since that's the kind of vocabulary we teach to children, too. But that got me wondering... is there an ancient children's book I could attempt to read?
Wait a minute, of course there is!—that's what Æsop's Fables is for! So I dug up a critical edition of the earliest version we know about—written by Babrius c. AD 200—and tried to see what I could parse. I can't read any of it yet, but I can make out enough words to mostly guess which fables are which, and even recognized one of the titles—"The North Wind and the Sun"—at a glance.
I suppose that's not bad for two months of work at maybe 15–20 minutes a day. If you're monolingual, curious about studying another language, and are interested in a gauge of how far you can expect to come in that time, there's at least a stake in the ground.