Normally, iOS devices use objective-c.
Normally, android devices use Java.
I believe that C# is the only option for windows phone.
Your best bet is probably C#....from a quick google search it seems to have the most multi-platform libraries/dev environments that support android and iOS.
It is also very easy to transition from C# to java, so if you want to make android apps in java later, you can do so.
Unity is a game dev environment that can output to many platforms, and also uses C#.
If you have never programmed before, you are a long time away from making any kind of "hit" game....therefore, multi-platform should be the last thing to worry about.
What device do you personally own and use? For starters, just focus on that device. Programming is fun, but if you shoot too high, it can also be a headache.
Stay gold, Pony Boy.