In the book Ready, Fire, Aim by Sean Pratt. Talking about sales should be your top priority from 0 to 1 million.
You have to think about what you are selling and where those people will be going. The Facebook and Linkedin groups are excellent for creating networks throughout. It's like an endless cocktail!
To better answer your question, you should really consider doing some research or even a SWOT analysis of your market. The different platforms are like different channels on television, tune that type of information. Ecom is different than B2B so it will depend. You will also need a slightly different approach for each one.
With all that is said, my best advice for you is to choose 1 or 2 platforms that you can really commit to on a daily or weekly basis and then continue with them and get involved in the community and develop relationships and create influence as you would in person. if you are in person Share relevant and useful information that someone thinks your type of products or services would like.
If you are looking for an additional benefit, consider: G +, Twitter, Facebook or Pinterest, since they are all indexed by Google, which will also help with SEO.
Hopefully this helps! If you are looking for more advice, you can check our podcast in iTunes, as it is aimed at all small business owners: