1. 
a
When a unit gets an item this trigger checks wether it is "youritem" and if it is then it adds the ability to the unit.
1.2 
a
When a unit gets an item this trigger checks wether it is "youritem" and if it is then it removes the ability to the unit.
2. First:
a
When a unit uses the ability this trigger checks if the unit is in the unit group "StandbyUnits" and if it is, it is removed. If not it is added.
Second: 
a
Every 5 seconds this trigger picks every unit in "StandbyUnits" and adds 5 gold to the owner of the unit for each unit.
3. 
Stack Items
This trigger checks if a unit already has the item when picking up a new one. If it has then the new one is removed. You can also use Hero - drop.
This are a lot of triggers... I think they all should work but I am not completly sure...