I had trouble with this as well and got no reply for my post but I did find that Using the Stop Ability and then from that using a trigger Event to process the action however my problem was that it only worked for 1 trigger, so if you did this it wouldn't work for 2 things.
Events
Unit - Any Unit uses Stop at Generic1 - Any stage (Ignore shared abilities)
Local Variables
Conditions
Actions
Player - Modify player (Owner of (Triggering unit)) Minerals: Add 50
Just open your trigger editor and create a new trigger, add a new event and find "Unit Uses an Ability" and fill in the remaining fields.
In actions create a new and scroll down to Player, Select modify player property and fill in the remaining fields.
Triggers are not hard to understand, they are after all a controlled language that if understood should work.
I had trouble with this as well and got no reply for my post but I did find that Using the Stop Ability and then from that using a trigger Event to process the action however my problem was that it only worked for 1 trigger, so if you did this it wouldn't work for 2 things.
Events
Unit - Any Unit uses Stop at Generic1 - Any stage (Ignore shared abilities)
Local Variables
Conditions
Actions
Player - Modify player (Owner of (Triggering unit)) Minerals: Add 50