I have a paid android app and i signed up for google Adwords to promote my app. I also selected “Get new users for your app” as campaign optimization. I was expecting Google to charge me only if the user install my app, Is my assumption correct ? I see the cost went up to 50$ immediately but with no installs.
You've purchased a PPC (Pay Per Click) campaign ad. This ad drives people to your install page on the Playstore and charges per ad click. Not per install.
If your ad is converting but your store page isn't - work on your store page being more attractive. People are clicking to view it but not installing.