Well - you could potentially have it out of plastic or steel, but yes, it wouldn't be nearly as effective and would tone down the amount of energy in a circle slightly.
I found my wand by hunting for it in the woods. I tried several - but when I picked this one up it just felt 'right' - and was all tingly and warm.
whee I warn you though: it took a while, but it's well worth it. Also, when I went to cut it with my bolline, (to shorten it) it didn't need doing - just snapped off in a way where you could put a crystal on the top.
However, I have yet to do this. >_>; I need to find a decent crystal first. As for putting crystals in - look at ones which properties you generally use. For instance, if you use visualisation then Lapis Lazuli would be a good choice - as would any third eye opener. If you're unsure about others, then take a looky at our
crystal guide.
I know that JVCA has put crystals into her wand - maybe you should consider PMing her, or wait until she gets back. ^^
Good luck, and happy wand making!