In fact, you do not need to seek social networks specialized in business. You can simply take advantage of the Facebook groups. There are plenty of business related groups, many of them are niche groups so you will meet there your target group very easily
Best Social Networks for Business promotion: 1. Facebook 2. Twitter 3. Pinterest 4. LinkedIn 5. Instagram 6. Reddit 7. Tumblr 8. Google+
There are many Social Media Channels that can help you for the same but t depends on your business, what type of Business you are running. Some Top Social Channels for Business Promotion are Facebook (You can share anything here as images, videos, stories, links, text etc.) Twitter (Share anything with your audience, it helps you to increase your brand value) LinkedIn (This one is for professionals and for Professional Use Pinterest (you can promote your business through images or infographics) Instagram (you can share your business images to promote your business or share the small videos with your followers, you can also share the story)