I have been trying to do a princess on a dowel. However, everytime i build it up it looks great then the dowel pokes through the head. What am I doing wrong? Should I be using fondant and gumpaste mix?

Are you using just fondant? It's too soft for making figures. Some people use a 50/50 gumpaste-fondant mix, but I use all gumpaste, at least for the body parts. I might use fondant with gumpaste or plain fondant for things like hair and clothes, but for the parts that need to hold up - and especially in the hot, humid climate where I live - only gumpaste will do. For things that need to be even harder (like a chair or table or fence, for example), I use pastillage (there are some recipes here on CC).