New to Substack - topic challenge

I started a Substack because it was the best way to express my thoughts. 

Recently, I grew an Instagram audience to over 12K followers, but i realized that IG become so fast-consuming and too plastic.

That audience is built around my expertise.

I want to start to write about stuff that I believe, the way i see the world, etc…

At the same time i want to help exsisting audience solve their problems and switch them to Substack too.

How to manage existing audience and building new one - for my personal beliefs and long-term.

If someone have similar experience or andle how to find a way for this solution, i would be very happy. 

What is the best approach?