1. An HTML/CSS editor (FireBug for FireFox)
2. Network Traffic Monitor (Foxmeter for Firefox)
3. Cookie Manager (Advanced Cookie Manager)
4. User Agent Switcher (for Firefox)
5. Modify Headers (optional)
6. Javascript Console
Those are your tools for debugging, writing some things.
Technologies you will have to learn...
1. jQuery
2. MVC framework
3. API/JSON content calls
4. AJAX
5. Cookies (same/cross domain)