well if you are sticking with web technologies then the JavaScript, JQuery, Bootstrap et al route is probably easiest.
I would probably also suggest you learn a server side language as well eg php, Ruby, Node, MVC and maybe a client side framework like Knockout, Angular.
It really all depends on what floats your boat and if you are looking to pursue this as a career then learning a server side technology is a must and is down to personal preference. I'm a Microsoft person myself so I would say c#.
As for JavaScript resources I can't recommend Jon Duckett's JavaScript and JQuery book enough. It has helped me so much over the past couple of months and is really easy to follow the concepts, language and features and is well laid out and presented.