Quick background: I'm a self-taught coder. I had dabbled with C++ a bit as a kid (12-13) but I didn't get serious until I was getting my masters at Stanford (a great place to learn iOS a few years ago before certain things became more widespread). I've started two mobile app companies, built dozens of apps, and now help entrepreneurs to design, architect, build, and deploy their apps into the marketplace.

You use the words design and build/code almost interchangeably, but as another responder pointed out, they are two entirely different skill sets. You'll learn some design along the way and then realize it's worth studying in it's own right.

So here's my advice (in no particular order):

1) In-Person Support. It helps a lot to have someone else to code/learn with, to ask questions of, to bounce ideas off of, and to celebrate your small victories with! I learned to code with the co-founder of my first company. We got dozens of job offers after we published our first set of apps.

2) Find a Technical Advisor. You will inevitably run into situations where you don't have a clue what you're doing and don't even know how to ask the question. Having a single person who you can pick up the phone and talk to is absolutely essential. My mentor created the shotgun apps for iOS and made some nice money in the process!

3) Digital Support. You know how you type "wiki" with your google searches when you want to go to the right Wikipedia page? http://Stackoverflow.com ("stack") will become your new best friend. There are a few others out there, but it's by far the best. Make an account and start asking questions. There's some etiquette on stack though. Vote up answers that helped you. Be respectful - there's a human being on the other side of the screen who's trying to help you solve your problem...for free (where as I could charge you $300/hr for lessons). Edit questions that are unclear. Give back. Always search before you ask a question.

4) Buy a Book. I'm not a huge fan of most coding book, but having an encyclopedic guide is really helpful when you're just starting. They have great examples and sample projects. They're also really helpful when you don't know how to do something the "right" (or at least better) way. If you're not willing to invest $40 in a book because of the money, then you're not really serious about learning to code or starting a company.

5) Work really hard. You're young so you can focus and bust ass on learning this. But you'll likely have to make some sacrifices.

6) Learn when to ask for help. I got arrogant a few months in and stopped asking for help. As a result I wasted a bunch of time, wrote crappy code, and learned to ask for help the hard way. One thing I do whenever I hit a nasty bug is to set a timer for 25 minutes (down from several hours when I first started btw). If I haven't figured it out by then, then I move on or start seeking out help. Having the discipline to hit your head against the wall for hours is a great skill. But that discipline is made 3x stronger once you learn when to ask for help.

7) Be okay with your first idea not succeeding. If you want to be an entrepreneur, then you'll have to learn 1) that failure is a good thing because you always have an opportunity to learn something when you fail and 2) that your early ideas suck compared to what you'll come up with in a few years after pursuing your early ideas and making a lot of mistakes. Even brilliant artists start out crappy. You hone your skills by practicing relentlessly. So start to embrace that it might take you a few times before you build a multi-million dollar company, but always fight and work like this is the big one.

I was 22-23 when I got serious.. and by serious I mean 10-14 hours a day, 6-7 days/week, for 6 months. That's what it took for me to feel comfortable with Objective-C. I didn't know everything (still don't), but I was no longer afraid of a new challenge. During the process, I was forced to learn PHP (server-side scripting language) and mySQL (database) and simpler things like XML, JSON, git, and other tools you'll inevitably need.

Here's the good news: Once you learn 2-3 languages, the rest only take a few days to get pretty good at. The syntax and vocabulary are all different, but there are only 3-4 paradigms worth learning.

In terms of specific resources. If you want to learn iOS, then you need to learn Objective-C, not Javascript, HTML, C#, and Lua - none of which are essential to launching a iOS app. Start by watching the iOS course on iTunes: iPad and iPhone Application Development (HD). It's about 20 hours, but a great way to get started. Paul Hegarty (the great) teaches this class and he helped write the language 20 years ago with Steve Jobs at NeXT.

One final piece of advice: iOS has started to peak. It was a great language to learn a few years ago because only a few tens of thousands of people knew Objective-C (Mac OX developers). Now, there are nearly a million apps in the app store and things are already crowded (and getting worse). Consider learning languages that are going to blow up in 12-18 months. I don't have any speculations about what's next, but it's something to consider.

The learning curve for coding is exponential so things will be slow at first but then rapidly accelerate as you have a basis upon which to build. Stick with it and it will pay off - it certainly did for me.

Best of luck.