Start the promotion with 10-15 installs per keyword in a 4-5 days campaign. Increase the daily number of installs in 1.5 times for those keywords which have reached top-20. Your first campaign may include up to 20 keywords. Stop it once some of the keywords reach top-20 and put them in a separate campaign with 1.5 increase in a daily number of downloads. Group all the rest keywords in a campaign and proceed with the promotion. Follow this promotion strategy till all the relevant keywords reach top positions and start to bring organic users.