Thinking it over, I think we can pretty much accomplish socializing during club sessions too. It probably changes who we would interact with though.
When it comes to affinity, I see more appeal to the Mock ICW and Dance clubs because that would fit with a charisma-oriented Shinji. Learning the way of rhetoric and moving with elegance both sound like a decent way to complete his repertoire, the latter might even serve in a more practical way if he can include some of that magic dance style into his fighting movements.
My personal preference though, I would rather go with Mountaineering since it adds survival points.
I don't want to double on potions that much and I'm not sure Shinji is ready to learn dueling from another teacher at this point.
I suppose I'll go with [x] Dance, since it sounds different from what we usually go for. And since we invested in luxury robes for important events and picked the charisma path, I think it's a decent pick. Even more so if you want more Amber point.