Hi Mike,
Welcome to the forums.
Be warned that it's going to take you around about a week of playing around to come to grips with how to start getting the best from the product! That being said, once over the initial learning hurdle, the software is absolutely brilliant.
My advice is to spend as much as your budget will allow. You won't regret it. Most of us on here seem to settle on the UltrPlusPAK because that is the cheapest package that has all Realtracks, Realdrums and styls. I personally started with the MegaPAK years ago and at the very first opportunity to upgrade went to the UltraPlusPAK and have been regularly upgrading that package ever since.
Below are some sales FAQs that you might like to have a look through if you have not done so already.
http://www.pgmusic.com/salesfaq1.htmAll the best,
Noel