set a class name per submit button

The easiest way to do this is to create your own custom styles based upon the css that is already present in the gravity forms system. You can add your own classes but it involves changing some plugin files that would revert back when you update the plugin through the wordpress admin.

To create your own styles, here are the css classes you need to work with...

This applies to all forms...

body .gform_wrapper .gform_footer input[type=submit] {border:1px solid red}

while this applies to the form with id=1...

body #gform_wrapper_1 .gform_footer input[type=submit] {border:1px solid red}

The above code was taken from http://www.rocketgenius.com/gravity-forms-css-targeting-specific-elements/#highlighter_125354