which are the best free ways for user acquisition and growth

Hi all,
You know ads campaigns can be really huge for an indie game developer.
So what is our solution for it
How do we survive in this big ocean?

If you wish for your ad campaign to stand out and increase your app's user base there is a handy Unity Ads Knowledge Base article on the best practice for optimizing your Ad Campaign.

Thank you for your consideration.
But there is a very big problem I couldn’t able to calculate yet.

You say campaigns lower than 1000 dollar / day is not recommended.
And someone says he had “millions of rewarded videos”/month in his game and he got only 2.8$ ecpm .
While the situation is like this how do you expect us to earn something?