Stardust and Candy limit
So far there has been no report about a cap on how much stardust and candy a person can have. Personally I have almost 4000 zubat candy and over 400,000 stardust. If there is a cap my best guess would be 10,000 candies and/or 1,000,000 stardust but I highly doubt there is one.
Source: Personal Experience.