Clans passed are offered space in the City as it is available. They join for the luxury its interior affords. The price may be too high, and those who refuse to pay it are ejected to the surface.
Unless you have allegiance to one of the City Kings, your clan lives outside the city with the other Surface Dwellers.
The city has no real goals beyond its own survival.
When you pick a faction you must also pick one of the organisations of that faction. The members of an organisation are responsible for making sure that part of the faction runs effectively. Your organisation will give you imperatives, which it will expect you to look into. The organisation also has resources at its disposal which as a member you will have access to. However if you disappoint your organisation enough these privileges will be revoked.
Organisations have requirements to join them; these include relevant skills which would make you a valued member, as well as ideologies and beliefs. If you do have a concept which doesn’t meet all the requirements please discuss it with the GM’s, as we may be willing to make an exception.