It depends on the condition of your App. Whether your App is a new one or not.
Let’s just consider two types of promotion, which generally suit two types of apps: for new and for those apps which have already been on the market.
If your app is a new one, start your promotion using the Package installs. This type of promotion will help your app start to have keywords coverage and you can then promote with keyword installs.
If your app is already on the market – it has its own specific keywords, and you can create a campaign for 3-5 keywords and promote them for around one week with hundreds of installs per day. Also, it is very important to remember that the effect will not last forever and if you notice that the rank is falling – you should also order the installs for visibility of your app at the TOP.
You can contact our support team to get more suggestions about app promotion.