Hi,
You will have to open gmail app and adjust settings for notifications of which there are many. Slide out control panel from left side after opening gmail app.
*scroll down to bottom and tap settings.
*now ta your gmail address
* find manage lables and tap first one.
*check each box you need,and set what sound for that folder.
*tap return when done,and tap next folder. You will do this for each one you want to be notified of incoming. I use same sound for all my folders,but you can have any available on device menus.
Reply here and ask more questions,I will get notice of your replies.