I want to monetize my app with ads without publishing it on google play store and app store (don’t have the money).
Is there a way for me to do so.
You gotta spend money to make money. 
How do you want to distribute the app then? Downloads and installs from non-official app store sources are miniscule. For ads to make you any money you need to have upwards of tens of thousands of downloads and frequent usage. You don’t get that without publishing on the official stores.
If you invest in developer access for it to pay off is achievable within a couple months. Mileages vary of course.