You can get a lot of the basics done with JQuery without knowing JS in-depth but you'll never be half as powerful with JQ without really knowing your stuff under the hood. Also, like regEx and SQL statements, it's a powerful tool but can also powerfully kill performance in a hurry.
I think it's okay for an experienced dev from another platform to start working with it but don't stop learning the core as you go and make sure you have an idea of what JQ is doing under the hood.
As far as stuff to learn ASAP, I would try to at least get a solid understanding of the DOM API and the ancestor/child relationship it banks on for accessing HTML and attributes, the cross-browser DOM API issues (particularly in IE before 9) that JQ normalizes (quirksmode.org is a good place for that information), and get comfy with the use of object literals in JS and passing functions around as parameters.
If you're supporting IE 7 or below, the biggest JQ gotcha to know is that there is no native document.getElementsByClass method working for you under the hood. Writing selectors like $('.someClass') will hit every single element in your document and throw logic + (I assume) regEx at the class attribute at the interpreter level in those browsers rather than native code the DOM API binds to under the browser's hood. This can be devastating to perf in large documents. Simply narrowing down with $('div.someClass') helps quite a bit but it's best to narrow down to the closest ancestor with an ID.
There's lots of tricks to reducing work avoidance in JQ selectors like using '>' when you can to prevent deeper recursion but that's the big one in older browsers.
But as I said, make sure you maintain curiosity as to what JQ is actually doing. You'll learn a lot about JS in the process.
