We perfectly understand that not all app developers and publishers have a significant marketing budget to play with. Actually, the vast majority of app devs are VERY limited in $$$ to spend on marketing. We know and respect that.
The beauty is that we make sure to provide app developers with practical training and recommendations that fit their budget.
Gladly, there are a lot of service providers and tactical options out there. We usually provide several options to choose from based on the available budget.