We all know facebook has the most users, but which social network is the most effective on a per-user basis?
That is very hard to say, and there isn't one better than the other. Each social network can be further used to gain readers and traffic. It all depends on how much time you spend on each one.
It largely depends on the target audience and target countries because Facebook might not be the first in the country
My advice to you is: fish where the fish are! When it comes to social media, you can’t properly choose your platforms unless you know where your customers are. Find out what social networks your clients use, where they like to get their information from, and what daily online habits they have. That way, you will know where’s the place to be in social media for your company, when it is better to approach your customers online and what information they might find relevant. For more information on the matter, you could read one of my articles: rogosocial.com/how-to-choose-your-perfect-combination-of-social-media-platforms/. Let me know if you need more information!
How can you be so sure? As the webtolight said: "That is very hard to say, and there isn't one better than the other". I totally agree with him, because it depends on what are you trying to promote and what is your target audience. Follow your potential customers