This is what I think is the best Ryze build out there. Total cost is approximetly 17,000 gold. You will end with about 2500hp, 4500mp and 1040ap. Ive tried it myself. If you set yourself in the right positions in team fights victory is only an R, E, Q, W, Q away. This build is made to cause extreme damage but it still leaves you with enough health to take a hit or two. One thing as Ryze is to be careful. He thought of as a vulnerable champion, so be careful of ganks. As well dont be surprised if your often being focused in team fights.
Useing your ultimate when on low HP against large crowds of minions in combinations with speel flux is a god way to sustaince your presence in lane or to quickly rejoin a team fight.
When fighting you want to go after the aquishy targets that are more vaulnerable to magic damage. Focusing tanks with allow their higher damaging heroes to kill you before you are
able to fight back.