Torment is alright. I wouldnt rush to upgrade your Guise and Ryze already wants/needs other stuff like bigger health/mana from Rod of Ages, Glacial shroud for CDR/armor, Abyssal or Banshees for MR/health.
Building Ryze as standard AP is kind of wasting his potential since mana items are more efficient in general.
Ryze also tends to use a Q,W,E,Q quick combo instead of spacing out his spells. This makes Torment much less effective. If you ARE going torment, then your defense likely sucks and/or no CDR and you CANT afford to go with your Q,W,Q,E,Q,R,Q,W,Q,E,Q combo.