For the most part use real world languages, Demons and Angels and the like speak all languages. Racial languages like elven and gnome you don’t need to worry about. Runes are done in runic which requires Knowladge Occult or Arcane as a class skill.
English – everyone needs
The following is a general list of some possibilities not necessarily needed nor exclusive
Dead languages – require a formal education of some type
If you have a language have a reasonable reason to have it but be creative you want just not absurd stay believable.