Q u o t e: How to create multiple waves - What i mean is... When wave one is finished and all Ghouls are dead, then a Timer starts giving players time to build up their defences, then once the timer reachers 0 Wave 2 starts with harder and more Ghouls.
Create Leaderboard with Point per kill system.
Use a "unit dies" trigger event. Whenever a unit belonging to the computer player dies, update the leaderboard for the killing player. Also, have a global unit group variable to which you add ghouls as you create them and then in the aforementioned trigger remove them from the group as they die. Once the group has no more units in it, start the timer that will run the next wave.