It actually depends on the match up. If you're not getting much lane pressure, and are winning then 
is bought first. It gives more mana capacity the more you cast, and then becomes 
which then gives you tons of mana to spam with, and a lot of AP. It's really cost effective, and allows for stronger, and more frequent harass. Then after your choice of boots, you get 
. Yes it's a slow build up as it's one stack/minute, but remember... You're getting more AP when you increase your mana capacity, and ROA does that while giving you more health too, and more AP, and it also restores it every time you level up. This allows for more building up on offense and defense while the battle goes on and you're alive.
However if you are getting alot of JG and/or Lane pressure then yes  is best first. You'll need that extra health and mana to be able to push back or sustain your lane presence while you wait for a gank or so forth. Then boots then  comes after. It still works either way though, and honestly I find  +  far better than  + . I can get roughly equal amounts of AP for less gold, but with more health, far more mana to spam with, a heal every level, more ease of building, and get more sustain with  's active all at once.
It's overall much more beneficial to what  truly is... an All-in AP Bruiser. Plus I can still build  + for more aggression and killing potential , or  +  for more overall damage and defense, or even other crazy combos to build into for say like CDR+AP, or things like that.
Basically with  with 10 Stacks and a  I get this :
214+ Ability Power
1650+ Maximum Mana
650+ Health
Active : Shields my champion for 150 + amount = equal to 20% of the mana I consumed for it
Healing and mana restoration every time I level up.
Flexible builds since I basically get both my offense and defense prowess boosted at the same time.
would make any good use of 
or 
. Yeah more AP is seriously more important and items like 
and 
are extremely useful, even necessary, but I ask this because Diana in her nature is an All-In champ that's melee oriented, and is in more risk to take a lot of damage in certain scenarios. Would the 20% spellvamp do any justice in her case and benefit from the damage based heals to keep her in the fight or not? It seems like it from what I tested but I don't know if it would be worth it. Anyone?
). For example, I take Morgana mid, with 5% SV in my masteries, and my 10% SV passive. I rush 
if they have a lot of MR, combined with her passive uping to 20% late game, I am running over %60 SV in the game, and is quite fun, as you can heal a ton with your Q and your soiled ground come late game.
but with more stuff added. Then you have 
(tends to change depending on games).
