Riedel is famous for being the inventors of the specialised wine glass. That particular grape varieties taste better in certain shapes of glass has been widely accepted for the past 30 years or so. However, this means that the array of available Riedel wine glasses can be somewhat overwhelming.
Your first decision as a Riedel purchaser will be which collection most suits your budget and taste. Once you have made that decision, the rest is much easier as you build your collection of grape-specific glasses within that range.
I've put together a few thoughts to help you decide which range is the one for you.