Consulting about implementing ad-classified engine from the ground?

Hi guys,

I’d like to implement a professional advertising classified engine in Ruby on Rails with cutting-edge technologies from the ground similar to Osclass [] but scalability as Craigslist, flexibility and customizability (integratable, theme customizable & plug-inable) as Spree.

I want to know your opinions about full of the project infrastructure. It includes about selecting best technologies for backend, middleware and frontend sides, best gems (authentication/authorization, theme customizable & plug-inable solutions, TDD, …) and so on.

Can anyone gives me your best advices? And please provide with resources for best-practice.


P.S. Maybe It will be an open-source project under MIT license.