PP, in this we need that old standby "Lewis and Short, a Latin Dictionary" because, like the OED for English, it gives every usage and shade of meaning, with quotations, though , of course, you have to have some Latin to understand those. Bit short (or lewis) on jokes, but it does find some words you wonder about: equimulga, a man who milks horses, for example, does create a picture of an aspect of Roman life which you'd never get from Gallic Wars or Ovid.
The grammar you have to learn. Kennedy's Latin Primer is still in print, for masochists. But the latest version omits all those amusing verses: "After si, ne, nisi, num, Quis for aliquis must come" was my favourite, but several had great lists of nouns which had some peculiarity, all fitted into verse. One included "winnowing flail", but for the life of me I can't remember what the Latin for that is nor what its fellow odd nouns were.
And for, what it's worth, I prefer atalanta's approach.