Nothing motivates me to join clubs. I wouldn't even join clubs of my favourite (friend-esque) models - it'd hold no interest beyond perhaps helping support a little. However, I don't really do that as I don't want to be the dependent who is turned to during leaner times. If they're reliant upon my contributions, then something has gone very wrong.
Anyway, enough about me
In my opinion you'd need to consider your audience, or more likely, what sort of audience you
want and what sort of effort you are
willing to put into it.
Is it purely fapping member? Then pics/vids. (for niche, substitute in costumes etc).
Is it for the personal interaction aspect? Then snapchat or private twitter account about life outside of your on cam time.
Is it for chit-chat? Then private message access.
You could probably create a fusion of all of that, but then you may get a fuck-a-ton of work to do
You could possibly create "levels" which include previous "levels" as bonus. But rather than ask what people want, I'd figure out your own boundaries of what you're willing
The last thing anyone wants is to pay money for a fanclub to find it half-assed as the person wants the money but not to put in the effort that goes with it.
Define boundaries/borders/comfort/willingness. Split it out into who it may appeal to, create groups, and possibly put limits on the numbers for each (i.e personal interaction may be something you'd be okay doing for 2 or 3 members... and if 20-30 members
want it, then it goes to the highest bidders?). Sure, canvass what people would like - but keep in mind that that may not translate into the views of many members
However, I've nothing to do with cam girls and or business so meh