There is plenty to learn in HTML5 without getting into the JavaScript APIs just yet. Once you learn JavaScript and feel comfortable in it, that may be the best time to tackle topics such as Geolocation, Web Sockets, Canvas, IndexDB, Web Workers, etc...
JavaScript is a dynamic and functional language, which is considerably different than C# or Java for example. So, please take your time and pick up the language. If you don't learn it appropriately you will invariably run into barriers down the road due to lack of understanding.
The jQuery library has been around for several years and has catapulted as one of the most used tools in the web developer's belt. The reason for its vast usage is that it solves many of the cross-browser issues that creep up during development.
If you find yourself writing more and more JavaScript and jQuery then you may want to consider picking up Backbone.js to help you organize your web application. This library is also a great fit for Single Page Applications (SPA). Backbone.js uses the familiar MVC/MVP concepts of Models, Collections, Views, and Routers. In addition there is a nice Event model, History support, and a Sync mechanism.