In general, for initiating classes I bring the initiation ability score up to 14 or 16. If its a Harbi, 18 is not out of the question.

There are a few archetypes I am undecided on when it comes to initiation ability score, since they retain their casting/manifesting. Nightmare most of all, since it actually uses that charisma for its power save DCs. I would have to use a 16 at minimum, but I don't know if the Nightmare would need higher. I might just have to roll one next time my group wants to run a one-shot and try that out.