I adore Riley, but only for a girl. I think Riley for a guy is *ok* but I wouldn't use it on a boy.
So, for a boy the only spelling I would use is Riley. For a girl I would probably use Riley, though I don't mind Ryleigh.
Rylea: There is so much potential for mispronunciation here. I don't think it's a pretty enough spelling to be worth the confusion, personally.