What's the most a single, average person can do to help as many people as much as possible?
Consecrate your life to being the embodiment of your own highest ideals. The only thing that is consistent in your life is you. By making this thing, your 'self', as insightful, compassionate, useful, productive, loving, learned, determined . . .[virtue X] you guarantee that all events and relationships you engage in will have this positive aspect. You can't control things beyond yourself, you can only contribute. The quality of your contribution is directly proportional to the quality of your person. Any specific set of actions, philosophies, philanthropies, 'causes' or the like are impermanent and only useful in a proper context and application. Therefore identification with or association of these activities as 'the best' will simply prevent you from actually being in the moment and responding, you will be reacting to your own idealized mental landscape. Moreover your knowledge of the impact of your actions is severely limited. However we might be aware of the impact of our actions in ways we can understand the butterfly affect of causality extends far beyond our awareness. Furthermore ideas are viral in their spreading. If others observe in you the embodiment of ideals they value and they see the effects of this in and through your actions they too may be inspired to refine themselves. This refracts throughout society as we inspire each other to evolve ourselves. To have a more evolved society we need more developed people to create it. To facilitate the development of others we can only lead by example, share the notes of our own growth journey and support each other.