Re: How many for a rookie?
BigCliff is right on target. Five different flies with 2 duplicates would probably serve you well.
Two other options: When I first fished for trout, I went into a local flyshop, bought a license, and asked the man behind the counter for a couple of appropriate leaders and ten flies that would work in the stream. He set me up with several flies that I know now are are old standards in trout fishing and a couple that worked really well in that particular stream. If you've got a flyshop in your area, that might be a way to do it.
Another possibility is to get a box of ten to fifteen assorted basic flies appropriate to the species. They have them in many shops and stores like Cabelas and Bass Pro.