I work professionally with Phonegap, so I can answer this question for you.
Can not do this without a Mac.
But why?
Phonegap uses the concept of webview. It creates a default spreading of directories and we develop normally as if it were a resposiva page. Phonegap is responsible for creating the project for the platform in question, distributing all the fonts we have written and plugins, and performing the project build / deploy for a specific platform.
The build is not magic, it simply uses the sdk that should already be properly installed on the computer. In your case, to build an iOs project you need to have the Apple SDK (XCode), which only runs on the Mac.
That's why it's not possible to do an iOS project on windows.
For information only, there are solutions that allow you to build an iOS app on windows, but these solutions still depend on a Mac as a server. I'm talking about Xamarin.