For personal use, I like Instagram than Facebook and Twitter.
But for marketing purposes: Facebook, Twitter, Google+, Pinterest
Because it works well for my niche..
Social Media sites are more important for SEM and SMO activities,Social networking sites such as Facebook, Twitter, and MySpace are become powerful marketing and communication tools.
Social media provides online communications channels in channels we do interaction, content-sharing, and collaboration. As we mentioned some or sites below:
No.1 Facebook
No.2 Twitter
No.3 LinkedIn
No.4 Pinterest
No.5 Google+
No.6 Tumblr
No.7 Instagram
No.8 VK
No.9 Flickr
No.10 Vine