I've never really understood AP on Ryze but the guide looks good enough for a first draft of sorts (+1 material that is) so I look forward to you're improvements. Eventually you'll need to include a section to explain exactly why you emphasize AP once you're starting to build your last items.

The trick is grater seal of replenishment. Try this and you'll see the difference :)

its "Q->W->E->Q" the passive makes it so your Q is rdy by the time u cast your E

I dunno how you play, but I always run oom with ryze without blue, even in late with 5k mana :/

Will try mp5/lvl instead of my flats and rushing Tear earlier

I like Ryze for high ultimate lategame power and i think this build uses this power. Hardly a caster is that durable and dealing such painful damage like ryze does. i just hardly play him because of the weak early. I have figured out that things such as easy enemies cant really exist for Ryze, against whoever i played (i didnt play against all of those you listed) i had BIG problems laning. Later on it was k but i think Malzahar in a lane will show you who is the god on the lane, at least if he is doing well. Having mastered the first 30 minutes you will become enormous dangerous.

Well but you explained everything corrected i like your item choices etc..
+1 from me ;)