The common misconception about ASO is that it will either bring about tremendous amounts of growth or none at all. There are those who whole-heartedly believe in ASO and those who shut it down altogether. As for me, I have friends who have built entire 7-figure businesses purely based on ASO so I know it works. But ASO is just a piece in your overall marketing plan; it is not the be all and end all.
To view how my clients are doing in terms of growth, I put together a Google spreadsheet and called it my ASO calculator. It shows daily and monthly downloads and cost savings. Through this tool, I would share to my clients that although you feel that you are gaining very few downloads in a daily basis, if the growth is continuous, by the end of the month, you would actually see that it adds up to something. And due to this, you get respectable savings which you can use for other marketing campaigns. That is the power of ASO.