Simplest doesn't exactly equal the best option. Follow any of the tutorials (or just read them) and you should get a good feel fro which is simplest. Simple is relative. Simple in terms of just getting to an APK, or getting one that works on Android or one that works with google play services, or acheivements, etc.. etc... Look at the manual and the tutorials and you can decide for yourself which is simplest.
For Android you have CocoonJS, Intel Crosswalk and PhoneGap. For iOS you have Ejecta, Phonegap and CocoonJS. Take a look at each one and decide for yourself which would be simplest for you. On a side note, all the iOS options require that you also have a MAC with Xcode ready to go.