I would hold off on any of these and actually work with vanilla JS + some jQuery. Once you outgrow those, THEN move to one of the above. The first 25% of most web apps won't need need anything past plain old Javascript and some jQuery. IMO it's better to learn the framework only when you out-grow the basic beginning tools, that way you also have a greater appreciation for the philosophy behind why some of these frameworks emerged.
If you're just beginning, and don't have a particular need for any one framework, I'd say go with Angular. It's by far the most widely used and popular of the choices (using github stars, # of modules, stackoverflow questions, github contributors, and github forks as indicators).
You're learning, there is no practical benefit in limiting yourself just to one framework.
Spend at least several weeks at learning all of them: Angular 2, Ember 2 and React. Learning by comparison will be much more beneficial for your understanding than doubling down on one framework.
I'm biased because I work on Polymer, but I'd say.... No framework - use custom elements.
Frameworks tie you into their silo, which is different and isolated from all the others. This is a terrible situation for developers (and ultimately users as dev effort is wasted duplicating things for each framework).
Custom elements are a way to define your own HTML tags. These work like other elements: they have attributes, events, child nodes and properties. They can be placed on a simple static web page, or wired together into complex apps. Elements are (mostly) naturally interoperable with other elements and even the plethora of frameworks.
Where Polymer fits in is that it's a library that help you write custom elements with support for templates, marshaling attributes, data-binding, etc. as well as some polyfills for web component standards.
It's very useful, IMO, but the real beauty is that Polymer elements don't leak to the outside that they're made with Polymer - they're just elements. If you use another custom element framework you can still use Polymer-made elements.
* The big caveat is this thing called Shadow DOM which is hard to polyfill. Polymer uses a near-polyfill called Shady DOM that can be important to use in some situations. It's still possible to interop with other frameworks with some configuration though.