What "Organic" growth strategies are there to increase users from 0 to 1M users and get our app featured on the Play store?

Background: We have zero marketing experience. We are a startup focusing on car maintenance/ marketplace for mechanics/services. We are about to launch our app and the aim is to generate significant traction to help us close our angel round and allow us to iterate our product. Our target users: 20-34, female drivers and new drivers, car enthusiasts. The feedback from beta testers is that "Word of Mouth" will be the most effective way of convincing them to download the app. We have not raised any investment capital so we have almost no money to spend on marketing…