Thanks for replies.
Playing a gold dragon sorc but rarely pull out fireball. Prefer twin haste on paladins (2 of em) or polymorph. I do sling firebolt a bit so + to hit and damage is pretty good.
Other meta is subtle which DM has ruled can be used with helm of telepathy, so fixed DC on that. Also have mirror image, misty step and counter spell. Not big on save or suck spells.
We have no cleric or bard or wizard so big hole in party spell casting with only sorc. Unfortunately I don’t have stats for ritual casting, hence the query regarding magic ini (bard). We don’t allow multi classing for this module.

Cheers and merry Christmas