Whatever you prefer, but the most balanced class is Raider - Gunner and then again what your preference for grenades is.
Though It is just what you like for the most of it.
Every new player should atleast tried to cap a few times so that they get used to the mechanics, for the rest again it is about what you like.
this is goldDownload, read, choose, and play.
http://www.mediafire.com/?2djy519nn3dipn5