ITC of gst on event organisation

Your question does not provide clarity about your business. Are in to the business of organizing Event or are you a trader participating in the event? please clarify.

In any case, since it will be for the purpose of the business, ITC will be eligible, provided that the place of supply of service will the place where the event is organized,

In case you are a trader and you are just participating in the event then, to claim ITC you will need to have registration of that state in which this event is organized.