I cannot find a Compose button in Gmail on my iPad mini or iPhone5

Hello cherries81,

Thanks for asking the Apple Support Communities for help with composing an email. I am happy to help.

If you are using the Apple Mail app, this info from the manual will help: Write an email in Mail on iPhone - Apple Support

Thanks and have a wonderful day.

If you are referring to the Gmail App, the compose button is the red circle with the white pencil icon. On an iPhone it should be on the right bottom corner.

On an iPad its at the bottom of the email list.