Want to learn to code for IOS and android, what language should I learn?

Not sure what language to start with for coding. Usually business ideas I have are for apps and I'm too poor to afford a developer and its high time I learn the skill myself. I am looking to make either social media apps or apps that serve some sort of function. I know it's kind of vague but I really want to learn this skill while I have a bit of free time on my hands. What books should I purchase as well? I would prefer to code for iOS first than move into the android space but if their is a language that does both than I would prefer that or at least become competent enough to talk code with out sounding like an idiot.