You should only be adding a spigot.jar and a projectkorra.jar as your build path, unless you are using some other library. And I don't recall AbilityModule being needed; must be something with the old API. As of now, for a basic ability you only need 2 classes: Your ability class then your ability Listener. Once you start getting more advanced you can create different classes for different purposes but the most basic of abilities will need these 2.
Your ability class will extend [Element]Ability and implement AddonAbility/ComboAbility/PassiveAbility/Whatever. Then once you fix the errors (creating the constructor, adding unimplemented methods, imports, etc) you should find that the rest is straight forward, if you've studied Java for a while.
Then of course your Listener will need to implement Listener and that's where you'll call the event that triggers your ability class.
If you're more of a visual learner you can always go to my GitHub and check out what I have imported there. If you need me to explain any of my code I'll be more than happy to do so. Hope this helps.
GITHUB