You have several options:
1) you can get the Google app and use Gmail from there (from within a browser window). The benefit to this is you get to see labels.
2) you can set up Gmail from the Mail app using the integrated Gmail option. The benefit to this is you can archive mail, as opposed to deleting it.
3) you can set up Gmail from the Mail app using the Exchange option. The benefit to this is you get new mail pushed to your phone (you can specify which folders are pushed) and all of your Gmail contacts are available on your phone.