Apple made it easier to see what apps are draining your iPad battery and hogging storage in iOS 9. To check you battery usage, navigate to Settings > Battery then tap the clock icon. This will give you a breakdown of your app usage and how much battery you most used apps are draining.
To view storage used, navigate to Settings > General > Storage & iCloud Usage > Manage Storage. This will give you access to all the devices connected to your Apple ID. Tap the "This iPhone" panel to view your apps and how much storage they are using. From here you can decide to delete apps you don't use, or decide it it's time to delete some photos from your Photo Library.