How to gain higher Market Share for your products where every one is competing to get their part of 'shelf space' (FMCG industry) with a zero Marketing Budget (No money spending like shelf rent etc)?

It's hard. Go back to basics and think about what you really want to achieve.  Do you care most about

- Getting net customers?

- Getting higher average spend per transaction?

- Getting more repeat business from existing customers?

Marketing is just communicating a message.  Think about who you are trying to communicate with, and be clear in your own mind about what you are trying to say. 

Are you using email and social media effectively?  Are you using offers and upsells effectively?  Could you improve your relationships with retailers?

What resources are there within the marketing team?  What skills and experience do people have that are not currently being used?

Can you work with production or packaging departments to create a more user-friendly product at no cost or even negative cost?

Do you market to and via the company's staff, shareholders and suppliers effectively?