I was struggeling with that GAplugin recently. So this is what I did:
1: if you're using phonegap build just place this in your config.xml:
<gap:plugin name="com.adobe.plugins.gaplugin" />
2: on the google analytics page create a new mobile app.
3: place the plugin in your index.html
<script src="GAPlugin.js"></script>
4: place the following code in your onDeviceReady function.
gaPlugin = window.plugins.gaPlugin;
gaPlugin.init(successHandler, errorHandler, "UA-12345678-1", 10);
5: track a page like this:
gaPlugin.trackPage( nativePluginResultHandler, nativePluginErrorHandler, "some.url.com");
more information can be found here:
https://github.com/phonegap-build/GAPlugin/blob/master/README.md