First of all you should decide which framework you want to use. The next step is to setup environment. Let's say you want to code with PhoneGap, than you need Eclipse and Android SDK, etc. The list of software you will find in a description.

Actually in my view it is not necessary to use jQuery or its mobile version for development. Sometimes you only need to create an up to 5-6 pages app with some basic animation which is easy to make with CSS3 Transition3D.

However, when you plan to create a big app with complicated business logic, than you may need to use some framework like Sencha or Angular (it depends on your needs).

Talking about frameworks you must understand that every framework is for certain purpose only. I mean, it is ridiculous to use, for instance, knockoutJS for big apps, because the only thing it has been developed for is data binding between model and view. Moreover, in many cases you don't need a framework at all.

Anyway, first of all you should to learn JavaScript basics. I mean how it works, in which steps a code is being processed, that is a function and what in a prototype and so on. Otherwise, you will never know how to write an effective code or how to optimize your code for better performance. It is critical for a mobile devices as they are not such powerful as a desktops. Also you need to understand how a browser works (rendering, network, etc).

That's my view.