The first point is this: you need flexible structure. You sound like a smart business person and you probably wouldn't allow any other part of your business to "take over your life," so why are you allowing social media to do that? You wouldn't allow bookkeeping to take over your life. You wouldn't allow email to take over your life. Don't let social media do it either.
Start by giving yourself a schedule. Pick two or three days out of the week which you will designate as your "social media" days. I am NOT saying that you should ONLY do social media activities on those days, but rather, those are the days that you have predesignated to be full-on active with social media. This will allow you to stay visible and keep your sanity.
The next thing is figure out where your market is and go there. If your market/audience isn't on Facebook, why bother? It doesn't mean that you should ignore Facebook altogether, it just means you don't put a lot of your energy there. And, if people invite you to networks that you're not familiar with or that don't resonate with you -- and your market isn't there -- hit the delete key.
Once you start to develop your own set of rules for managing your social media initiatives and stop allowing social media to manage you, you'll be golden.
Also, if you're still stumped about what you should do, you might want to download our Social Media Strategy Blueprint workbook, which is available free from our website at: http://www.xynoMedia.com. Fill out the form on the left and the workbook will be sent to you straight away.