如何在各种设备上保持Android布局一致？

I am new to Android Programming, I just published an app on playstore and found out that few buttons that I put in my layout doesn't show up on some of the devices. How do I make sure it is consistent across various devices? Should I avoid using relative layout. Here is the layout where Create Account Button shows up on Galaxy Tab, Nexus 4, and 5 but not on Galaxy Grand.I am new to Android Programming, I just publish