A very sound decision. Regardless of application and render engine, having a good grasp on materials/shaders and lighting (you really can't separate the two) is very important to get the results you want.

I can't point you to any other resources or learning materials, I just wanted to give you a bit of encouragement for your decision. Also, keep in mind if you're planning on using unbiased renderers like Lux or Octane in the future, you will need to learn the lighting and materials specific to those products. I find lighting and materials in both Reality3/Lux and Octane to be much easier than Poser, but others find Poser much easier, so it is a bit of not only learning the mats/lighting, but also finding what works well for you.

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