This will depend on your target audience. If the nature of your business is for B2C (business to consumers), our first port of call would be Facebook and if the nature of your business is for B2B (business to business), our first port of call would be either LinkedIn/Twitter. This will also depend on your existing followers. 

Here is a useful article for further information: https://digitalmarketinginstitute.com/blog/2017-11-30-which-social-media-platforms-should-you-use-for-your-business.