Stop for one second and think about what Social Network actually means.
Social: Pertaining to, devoted to, or characterized by friendly companionship or relations
Network: An association of individuals having a common interest, formed to provide mutual assistance, helpful information, or the like.
My point? Having a Facebook page, Twitter Profile and YouTube account does not a social network make. You have to use it. Coldly firing messages into the ether like ‘buy my record’ and ‘come to my gig’ will have limited success. It may be that you don’t want to be all chatty with your fans and retain some mystique but at least provide regular an interesting content that will engage your fans to talk about you and your music.
No amount of fancy, all singing, all dancing social networks will make up for shit music or a boring artist. As to what to use, check out my default setup here.
Great music plus a network of engaged fans = career
That is all I have to say.