Diana Scorn of the Moon is really strong pick for almost any team. Her kit allows her to engage the enemy team and easily disrupt while dealing a lot of damage. You will have to build her quite tanky since you should almost always engage team fights with her.

Attack speed Marks
I like taking these to trigger your passive more often which can deal a decent amount of damage. If you want something else taking magic penetration marks.

Armor Seals
Good against all attack damage dealers. You pretty much will need these.

Ability Power Glyphs
More damage output

Ability Power Quintessences
And again more damage output

Sorcerers Shoes For magic penetration and movement speed.

I find that the Ohmwrecker is and underrated item not for the active but for the stats it brings to the table, 350 Health, 50 AP, 15 Health regen/5 and 15 Mana regen/5. The active is just a bonus for the ability to tower dive if needed. And the Philosopher stone is good for a little more gold income.

Abyssal scepter because you will always be in melee range. Increases damage output effectively so.

Liandry's Torment for Hp, Ap and Magic pen. The other passive is also a cool bonus.

Zhonya's Hourglass gives a ton of Ap and good amount of armor for extra tankyness but the key to this item is the active. Use it wisely....

6th Item depends on how your team is doing. If you are doing really good go for Nashor's Tooth for more attack speed and Ap or Rabadon's for even more Ap. If you need to be more tanky you could go for Rylai's Crystal Scepter for more health and Ap or Iceborn Gauntlets for Ap, armor and the Sheen passive.

This guide is still in the works. Give me some time :)

First guide btw