Cassiopeia: Rod of Ages OR Seraph's Embrace + Rilay's Crystal Scepter?
I used to build Rod of Ages + Seraph's Embrace for a while, then I understood how useful Rilay's Crystal Scepter was and decided to build it + Seraph's Embrace. Probuild, anyhow, suggests building Rod of Ages and, situationally, Rilay (with a smaller build rate for Seraph's Embrace). What do you suggest? Which is the best build order? Is Rod of Ages' mana sustain sufficient for extra-lane business? Is Rilay's Crystal Scepter necessary (I had a game a few hours ago without it since I had to build additional MPEN and MRES and I felt quite lost u.u)? What about Seraph's Embrace? I build it because of its sinergy with E's mana passive, the glass cannony AP it gives and the shield.
So what? Pls explain your suggestions u.u