Here's the thing -
Almost no one_ _is doing new work in jQuery. There's a few small projects around, but I haven't seen a big-budget project that uses jQuery for a while. I've also seen it used for prototyping.
It's still really useful to know: because there's still tons of legacy jQuery code around, and understanding it will be necessary to work on updating legacy projects.
So, I recommend learning enough jQuery. Understand how the selectors work, and the $(document).ready() pattern. After that, learn as the need arises.