I have a gmail account setup on my phone (lumia 925) and I have noticed that when I delete an email using the mail app it places it into a newly created "Deleted Items" folder instead of the trash. Is there a way to change where deleted emails go?
This is the default behavior for the mail app on Windows Phone 8.
As an workaround you can search for a Gmail client on the Store. An specific app should met more some aspects of the service better than a general one.
As a suggestion I recommend you take a look at MetroMail.
I know it probably is not exactly what you want but a general purpose email client never will met all requirements of every single email service. For example it not provides option to chose aliases that is built-in in Outlook.com.