Revert to 9.3 from 10 beta 1
Well, If you don't have a backup of iOS 9.3, you might not be able to get your data back. Haven't tried it, but if you downgrade, and then set it up as a new device, and then restored your data from iCloud, you might get your data back. Don't take my word for it.

Also, you will need to have access to a computer running iTunes. You cannot go back to iOS 9 without it.

To downgrade to a fresh install of iOS 9.3 there are a couple of steps, and you need a good internet connection, a computer with iTunes, your device, and a cable to connect the device. 


Head over to ipsw.me (On a Computer) and download the latest iOS 9.3.x ipsw
still being signed by apple (It is in green) for your device. As of July 8, iOS 9.3.2 is being signed by apple for all supported devices.
Connect your iDevice to your computer running iTunes, and make a full backup just incase. (Worst case scenario, you'll have to go back to iOS 10 if you don't get your data back from iCloud). The download is 1-2 GB, and it might take a while depending on your internet speed. 
Go to the Summary Page of iTunes (Should automatically show up when you connect your device and open iTunes).
Alt+Click the "Restore" button (On a Mac, option+click), and select the ipsw file you downloaded earlier.
After a while, it will have restored your device, and you should be back on a clean copy of iOS 9.3.x.
Try restoring your data from a backup on iCloud, or try from the full backup you made earlier on iTunes. It will restore your data, however, I have no clue if it will take you back to iOS 10. (Again, worst case scenario, you will have to stay on iOS 10, and you won't lose your data since you have 2 working backups on iCloud and iTunes)

Remember, don't try out beta software, especially not the first beta. If you do not know what you're getting yourself into, or if you do want to try out beta software, do it on a different device or make sure you have a working backup before you jump ship.