The more events you'd like to organize, the more popularity you'll need to gain. Here are two ways for you to increase your popularity level:
Invite new mayors to join Fortune City: Tap the Civic Square, then tap the "i" icon at the left and tap Upcoming Events. Tap Invite New Friends to view a link you can use to send to friends on social media, or copy the link and send to friends directly for them to download Fortune City for the first time. Each new mayor who downloads Fortune City using your link and registers an account will increase your own popularity level.
Use diamonds to quickly increase your popularity: Tap the Civic Square, tap the megaphone icon at the right. Then tap Use Diamonds underneath your popularity target to spend diamonds and immediately increase your popularity level. If you don't have enough diamonds to use, you can tap Visit the Shop to purchase some!