To clarify an earlier post:
- you cannot have a guild and class that conflict.
so: no paladin class jester guild.
so: no monk class bard guild.

- you CAN have a guild without joining any class
(though that would seem unwise, as you would have no skills
beyond those skills available to all)

- you CAN have a class (monk, magi, sentinel, whatever) without
being a member of a guild. In this way you could have skills,
but you miss out on the potential advantages of a guild -
shared experience, a group to help you out, guild hall, better
access to training, and all the advantages of being part of a
group that works towards shared goals.

I hope that helps!

Penned by my hand on the 3rd of Lupar, in the year 391 AF.