To answer both your questions:

1. How to start with plugin development:

There is a decent tutorial for an hello world application inside eclipse: Help -> Cheat Sheets -> Plugin Development. To start I would also download the plugin ide, just use the normal installer from the website and select Eclipse IDE for Eclipse Committers.

2. Missing dependencies

Adding these dependencies to your classpath is not enough (propablu not event needed in this case), you have to add the to you plugin.xml. Open the Manifest.MF and have a look at the Require-Bundle are the dependencies added there? You can also use the Dependencies tab in eclipse.