There was another thread about this a while back, and I'm just going to link you so you can get an idea of people's various opinions on the matter. Note that the thread eventually fell to bickering between some of the various parties involved, and it will really not do any good to read past page 2.
http://forum.shrapnelgames.com/showthread.php?t=46214
Alternatively the short version - It doesn't really matter what nation you play as, as long as you enjoy the theme of the nation you'll probably enjoy playing. But if there was a nation I would describe as the easiest for a new player to play, it'd probably be EA Niefelheim. They are strong or capable in all categories and one of the more forgiving nations. They can be played bless, scales, rainbow, whatever. The only drawback is their best units are all cap only, and the rest are only average at best.