App Optimization (devices)

Hello! Greetings to all. I would like if someone knew what process to follow or where to start for the issue of making my game compatible with as many devices as possible. Because it is a very big problem when you can not reach more people because they do not work the game on devices a little more media or low range. Even sometimes in very good cell phones, something weird.Thanks in advance !!

I leave here my application link in case someone wants to tell me if it works on your device:

You should have a low range device to test on, old Android devices are practically free.