P.S. About investment in tutorials: if you can find samples videos from both, compare Infinite Skills to Mark Bremmer's tutorials - they cover similar things, but there are some differences, so I'd look into it to see what's the best fit for you.

Also, most DCG plug-ins are a very worthwhile investment. Things like Shaders Plus, Shader Ops (1 & 2), Anything Goos are must haves in my book. There are also very useful Shoestring Shaders. And Toon Pro can be extremely useful for a variety of looks, not just strictly toon. It's not that you absolutely wouldn't be able to do without them, but they make life much easier and some very cool things possible.