Craig Newman started Craigslist by listing events taking place in San Francisco. Jerry Yank and David Filo began Yahoo as a daily list of interesting web links. Mark Zuckerberg started Facebook for Harvard students to share their profiles.
These huge community-based empires began with single, useful, actions. There were no grand plans. No strategies for growth. No objectives to determine success or failure.
This is the missing secret of starting successful communities; do a single useful thing. Then keep trying to be better than you were yesterday.