As an event organizer, What key metrics will we use to determine success?

Money ($, euro,ets) i.e - Profit

first of all you have know about your customer behavior. what the tools and quality customer likes then you can easily use marketing keys. you can easily plan strategy which way your customer suit best.  

Revenue and Reputation of the event

customer comes first but if u want to go all the way , marketing is your key .

We can determine the success, when you give all your best to your client and your client is highly appreciated and satisfied to the service that you give. And will spread the good work you did to their friends and relatives.

time planing would be my periorty