Every app and keyword is individual, so a different amount of installs is needed for each keyword for each app.
Number of installs you need for promotion depends on the keyword difficulty, number of current organic installs of your app, on the conversion rate from view to install for this keyword for your app, etc.
The higher the score of a keyword is, the more installs you need to move the app to the top. If you need help, you can contact our support team or personal manager, and we will choose the best keywords and strategy to promote them. You can also read article about this in our blog.