How to choose the best social media for your business?

Use whatever networks your audience is most active on. You can go to BuzzSumo, enter several phrases pertaining to your niche, and see where people are sharing the most. A big part of it is dependent on what you're "selling" and what type of dialog/engagement that you want to have with your audience.

From there, you need to really nail down who you audience is and who the influencers are by network. Once you who those two key elements are then you can really make a decision about the networks that you want to focus on so that you're not peanut buttering all the channels.