Gluttony has usually been Flanderised by the media into being simply overconsumption of food. The original Biblical definition of gluttony is actually tied to any kind of luxury, reflected in what Piper does. Note that to be a glutton, the sinner must also be wasteful. Piper indulges in endless luxuries without a thought to her finances, and without actually enjoying the things she gets herself.
Pride can only be defeated by Prue getting saved by someone else. As pride's good counterpart is humility, this makes sense.