The best mount ingame is the special horse for the dragon seeking quest. I forgot what it's called cause when I played, it was on Maylasian-Chinese like 4-5 months ago.
It's the most difficult horse quest and can take ALOT of money and very time consuming. Can take up to a month. Just so you know, that horse is better than cash shop mounts. But the question is... is it worth the money and time?