I think you should learn basic drawing first, it will help you lost. My friend tells me that when I wanted to learn drawing. I realize it is true.
If you want to draw with pastel pencils I recommend you Stabilo Carb-O. They blend great with your finger, pastel blender or q tip. They erase easily with a chalk eraser. These do work well with water but the colors aren't as brilliant but still beautiful. These are on par with Derwent pastels, in fact, some of the colors are considerably brighter if not using water.