This plugin adds a placeholder field into your Gravity Forms input and displays it as a proper HTML5 placeholder attribute without JavaScript (yaay!)

I took code from this article from wpbeginner.com and optimized it. Applause to them.

Do I need to implement jQuery somewhere?

No. This plugin works fine without adding jQuery to your theme.

1.2

Added support for textarea

1.1.2

Tagged wrong version, sorry

1.1.1

HTML entities converted correctly

1.1

Fixed that the generated input had an html wrapper

1.0

Init

1. Upload placehold-gravity-forms.php to the /wp-content/plugins/ directory
2. Activate the plugin through the 'Plugins' menu in WordPress
3. Done. Check out your Forms in Gravity Forms.