Pastels are fun! ...very, very, very messy though, so I don't often work with them. The last
thing I worked on wasn't even finished because I got bored with the concept behind it. XD;
Let's see.. Cheap pastels don't really matter, imho. It's the paper you've got to watch for. Using some paper that allows for super easy smudging can be a good or a bad thing, depending on what you're going for.
I prefer a rough method as opposed to lots of smudging. That is--put it down as you mean it to be rather than smudging it in. Smudging will happen naturally as you work on the piece. I usually start with the darks and just put them down only where they're needed. Then I go to the midtones and put them everywhere, and light (usually just white, as I don't have an extensive pastel collection) ontop. Go back and retouch if needed, etc.
I'm a huge fan of contrasts, so I vote for not skimping on it. Lots of lighting and shadows! ...unless, you know, it's supposed to be a dim lighting setting. It'd probably help your colorscheme (which isn't bad, imho--I don't think it conflicts with the color wheel theory or anything) if it had lots of shading. :.D
Um. Tutorials might help you better than I could.
Pastels
Color Wheel
Shading
...and many more via Google search.