Initially, I was focusing on feature development on the discovery/search side, but after speaking with some initial groups - none of them cared about discovery (although being found easily would obviously be great for them too) - they just wanted a place to be able to gather RSVPs for events, and a page to post events on easily.
So, the plan is to focus on the organiser side for now and open up discovery if/when I see there's enough demand for groups to actually use it, and we have a good amount of events.
As for launching in every locality - I had planned to focus on one geographic area at a time but that's something I'll need to think about more. I've seen a few different approaches to search, like having pages dedicated to cities/countries rather than just a single search page - that seems like a good intermediate step to have before going all out on a single search page.
RE: monetizing - the rough plan for now is just to have some premium organiser features, which would be aimed at larger groups.