I'm definitely no expert on social networking, but for me, Twitter is my favorite outlet - I can hook up my Facebook author posts to it, and also send my Pins to it, not to mention connect my blog to it directly, and my Tweets directly to my blog.
But the best thing about it is that you can reach a large group of people without having a large following ... as you follow others (I try to stick with writers, publishers and book-related groups), you can do a couple things - you can reTweet interesting items from their lists, which puts you on their radar, and you can piggy-back on their followers by posting relevant/interesting items and then adding their handle to it. i.e. @atrandom is the Random House handle, so if you write a blog post about one of their books you like and then Tweet about it with their handle, it will go out to all of their followers (I hope that makes sense).
Also, I find that people who are on Twitter want to interact, and I've made connections with many writers who I don't think I would have met in other ways. I agree with you -- I'm overwhelmed with social networking, but as a writer I find Twitter more useful than Facebook (the latter seems to me to work for corresponding with friends).
Hopefully this is helpful; if you'd like to correspond further about it, I'd be happy to.
Thank you, Kim. That is extremely helpful. Once my kids are back in school, I may just make the plunge.