As a front end developer the things I would advise someone new to get into are: HTML5, CSS3, jQuery, WordPress + Git(Hub) on the coding side && branding, copy writing, color theory + good UX/UI principals on the design side.
Edit: Some server admin stuff [ cpanel, phpmyadmin, dns ]
Hope that's helpful (:
Having just started diving into front end web development, I'm personally finding java and jQuery super useful. I'm also getting excited by some of the new things HTML5 has to offer.
jQuery. x100. If I had to pick one tool for a front end developer to know, it'd be jQuery/Javascript.
jQuery and Bootstrap. Learn how to make Ajax calls, and get comfortable encoding/decoding JSON.