IOS and Android are so different, so if you wanna start, make your choice! If you like/use java try Android, IOS is on Objective-C. Also, for IOS you need a mac

IOS and Android are so different, so if you wanna start, make your choice! If you like/use java try Android, IOS is on Objective-C. Also, for IOS you need a mac for development SDK, for Android any os is supported. and then search for tutorial and quick starts, the net is full :) enjoy!