If I could give you some unsolicited advice, I'd say focus on learning how to
program, and not on a particular language. Use whichever language will help you to program the best. Once you understand programming, particularly in the functional paradigm, picking up a language like Arc, or Clojure, Python, or Scala is a quick study (ok, maybe not Scala).
If you think Arc will help motivate you to learn to program, and has sufficient resources to teach you, then by all means go for it. Otherwise, there are a lot of similar language that have tons of learning resources. Racket in particular, as well as MIT Scheme, are two languages related to Arc, both with great, open-source books (How to Design Programs and SICP) that teach you how to truly program, not just hack up a web site like many programming books do [1, 2]. Really, these are probably two of the greatest programming books, albeit with very different teaching approaches. And like Arc, both of those languages are schemes, or at least very close.
Finally, one additional unsolicited word of advice: don't put off learning data structures and algorithms (particularly their time and space complexity). Both of the two books above will teach you the fundamentals of these topics. I'm a self-taught programmer who put learning these things off for several years, saying to myself, "eh, I don't need them, what do they have to do with real programming?". I confused them with the "interview puzzles" everyone was (rightly) criticizing.
Well, I was wrong, and now that I have a better grasp of the things a good CS education can give you, I'm advancing at a much quicker rate, and I understand programming at a much deeper level. I wish I knew back when I started teaching myself that these were important things to learn. Coursera has some excellent algorithm courses. Khan Academy also has some very good algorithm learning materials [3]. Finally, VisuAlgo is an excellent site for visualizing algorithms [4].
In addition, if you ever decide to become a professional programmer, you'll have to know algorithms and data structures for most interviews.
1. http://www.ccs.neu.edu/home/matthias/HtDP2e/index.html
2. http://mitpress.mit.edu/sicp/full-text/book/book-Z-H-4.html#...
3. https://www.khanacademy.org/computing/computer-science/algor...
4. http://visualgo.net/