Ignore standard (and popular) BS of "promotion through blogging and social networks", that's a myth. A successful blog is a business on its own. PR companies have full-time bloggers, Facebook "friends" and even wikipedia editors to spread the word about their clients, and it will cost you serious money: on par with several full-time yearly salaries. And don't expect to become a Facebook after spending that much. Building a brand in consumer-space entertainment business costs millions of dollars (and some luck, still)
That is a bitter truth, assuming you're after building a sustainable business. That doesn't apply to you, however, if all you need is to get a couple thousand "early adopters", living mostly in Bay Area, create some awareness of what you're doing in SV-circles, hopefully reaching an ear of a potential acquirer so you could flip it for a few million, then hire a good SV-connected PR firm: that will cost you $10-20K/month or get admitted to YC and their PR machine will do the trick.
That is a bitter truth, assuming you're after building a sustainable business. That doesn't apply to you, however, if all you need is to get a couple thousand "early adopters", living mostly in Bay Area, create some awareness of what you're doing in SV-circles, hopefully reaching an ear of a potential acquirer so you could flip it for a few million, then hire a good SV-connected PR firm: that will cost you $10-20K/month or get admitted to YC and their PR machine will do the trick.