Hard to say, definitely more than 30k USD. These days around 90-130 USD per day. I use many different ad networks.
If I would be you, I wouldn't just stick to one network. Don't make the mistake and stick with Google Admob only, it can backfire a lot. You might end up losing all your money and your account. Happened to me as well last year. Just few hours before pay out more than 4k USD they terminated the account. I also use Unity ads and FAN, never had any problem with them. Yes, the eCPM is lower and the fill rate is lower as well, but they are way more reliable and you don't need to expect any random ban or termination.
So in order to fix the low fill rate (which is around 75-90% for me on FAN for Android) you can use Appodeal or another mediation. Sign up for a few Ad networks for example Admob, Facebook Audience Network, Unity Ads and Applovin. Set up the mediation in a way that you will get the most possible revenue (waterfall).
If you plan to buy app installs make sure you integrate Firebase, Facebook SDK and Appsflyer. Its extremely important to know your numbers in order to scale.