Should i spend time preventing piracy of my app?

The title says it all, the more i do research about piracy and the Tools used to crack an app the more i think it is just wasted time.

My biggest threat is that my app is being cracked and uploaded again within minutes after i released it. But i'm not sure how harmful it will be to my Revenue, if there even will be a Revenue. Maybe someone can come up with some experience, it's my first app which i'm going to publish and i have no experience with that. My app is going to be free with ads. I think this is another line of defense because in my opinion, the main Focus is on paid Apps due they are not available in a lot of countries..

My current Approach is that i will just use proGuard not really to make it harder to crack(more likely understand the code), because you don't even Need to understand the code if you just simply resign it and upload the same application to the playstore, you will just Need to Change the packagename. My main Point of using proguard is just to shrink the app.

Is this a "good" Approach?

Any experience is appreciated.