Immediate issues I see:
- you should have 10% CDR from masteries, and your Q gives you another 10%, so ice gauntlet + frozen heart put you over by 15%. Thats wasted stats.
- in my thread I discuss muramana--I think seraph's is better
- merc treads are by no means terrible, but I think sorc shoes are superior on Ryze unless you are facing a whole lot of CC.
- mercs -> sorc shoes
- ice gauntlet (or frozen heart) -> rod of ages
- banshees -> abyssal scepter (or void staff or Liandry's Torment if you really don't need the MR)
- muramana -> seraph's