If you want guaranteed results, use a cost-per-install campaign. I work at an ad network that specializes in these kinds of campaigns.[1] You'll have to pay a lot per-install, considering how poor conversions are going to be. Our network automatically calculates your eCPM on the fly and will rank campaigns according to that—and so too it works with most competitors' network.
To be honest, with your tiny budget and a two dollar app, there's no effective way to spend your money with a positive return on investment.
To be honest, with your tiny budget and a two dollar app, there's no effective way to spend your money with a positive return on investment.
[1]: http://chartboost.com