You have to be careful with Javascript - IMO there are lots of "bad" ways to use it to write code. Ways that are unmaintainable, bug-prone, etc.
I would start by using it with an MVC Javascript framework such as Backbone, Ember, or Angular. Of those, for a new person I would probably recommend Angular as it really puts a lot of needed structure around your Javascript code and minimizes the amount of JQuery you'll need to know/write. And it's a pretty small library to boot but can do some powerful things for you.
I think though to get "satisfaction" from writing a Javascript client you'll probably end up spending as much if not more time learning CSS.
Also, look into using Bootstrap as well (can be used in conjunction with other libraries like Angular).