Not sure what you mean.  Are you asking how to cost them?  If so, it depends on how you want to build your army.  You just need to decide if you want them to be heavy or light and what level to make them.  For my Macedonian pikemen I usually make them Heavy infantry - Veteran and sometimes I add the Disciplined ability.  Not sure about the celtic warbands.

That sounds good for the fantatics.  Another option to use would be beserker.  You could try both and see which one you like best.  I think that's what makes the game cool;  you can change your army to fit the situation.  Have fun.