There are many different types of event planning apps that you can build for your startup,

Initially, the concept of event planning software was only limited to serving big event organizers and event management companies, but then the entire landscape of the event industry changed with the introduction of Eventbrite.

It was one disruptive Idea which made the event planning a child's play,

Eventbrite has given some of the answers to unthinkable questions;

Accessing an event management application form the web.
Generating and selling tickets in just a few clicks.
Automatically promoting the event on social media.
Browsing and creating events form a single event.

Eventbrite provided all the features you would want for planning your event with a very simple and easy user interface that’s what lead to their success.

So it is about utility while developing an event planning app you have to make sure, you maintain the balance between the features and the ease of use. Sometimes it happens that developers try to stuff out lots and lots of features and it leads to their failure because it affects the user experience very adversely.

If you are looking for developers or information regarding building the event planning app, then you must check out this page Eventbrite Similar App Development.