Hey Guys its me, Knirpsipirpsi, I'm from Euw and playing since about 4 Years.
Diana was my Midlane Main Champion for a long time, but due to the new Guinsoos and the Season 6 changes, I started playing her in the Jungle, and its completly CRAZY o.O So here's my short Guide on How to play Diana the best way ;)
I Hope you all enjoy reading this little Guide, and if you have any Questions or Comments, just write me!

Knirspipirpsi, aka Joschua

Passive-Moonsilver BLade:
Diana permanently has 20% bonus attack speed, and cleaves nearby enemies for 20 - 250 (based on level) (+ 80% AP) magic damage on every third basic attack within 3.5 seconds.
Tips: Very Simple here. More AS=More AA=more often your passive. Thats all you need to Know.

Q-Crescent Strike:
Active: Diana unleashes a bolt of lunar energy that travels in an arc, dealing magic damage to enemies hit and afflicting them with Moonlight for 3 seconds, granting Sight of them for the duration. Magic Damage: 60 / 95 / 130 / 165 / 200 (+ 70% AP)
Tips: Use it to gain Vision of your Victims before they enter a bush or becoming sealth.

W-Pale Cascade
Active: Diana shields herself for up to 5 seconds and creates three spheres that orbit her for the duration, detonating upon contact with an enemy and dealing magic damage to nearby enemies upon detonation. If all three spheres detonate, Pale Cascade's shield is reapplied, stacking with its original shield, and its duration is refreshed. Shield Strength: 40 / 55 / 70 / 85 / 100 (+ 30% AP)
Magic Damage per Orb: 22 / 34 / 46 / 58 / 70 (+ 20% AP)
Tips: Use this in every 1vs1 or when you are fighting! This Spell keeps you alive!

E-Moonfall
Active: Diana reveals and draws in all nearby enemies to her location, slowing them for 2 seconds afterwards.
Tips: You can stop channeling effects with that Spell like Nunu ult.

R-Lunar Rush
Active: Diana dashes to the target enemy, dealing magic damage.
If the target is afflicted with Crescent Strike, the effect is consumed on all enemies and Lunar Rush's cooldown is reset. Magic Damage: 100 / 160 / 220 (+ 60% AP)
Tips: Use it after your Q, so if they flash away you can Jump on them again.

Here are some short basic combos you need to know:

Jungling: Activate W, Hit everyone with Q and try to hit as many as possible with your Passive

Ganking: Q-R-W-E-AA-R(If they try to escape)

A useful Tip: If you are fast enough, you can use your R and Q midair to gain the reset. Better try this in a custom game first!

Pros:
+High Burst
+Good Shield
+Amazing 1vs1
+Mixed Dmg
+High Mobility
+CC on her W and E
+Assasin, Tank and Fighter



Cons:
-Not the best pre 6 jungling
-Cant gank pre 6
-No real escape

As you see, I prefer Fevor of Battle on Diana, because it makes your AA even stronger. Magic Penetration is aswell better then the Armor penetration, cuz your passive on every 3rd AA deals magic dmg, like all of your abilities.

Here its a mixture of ad, ap, as and resistance.
You can choose from that 4 classes anything you want. My prefered Runes you can see on the top.

So, as I said, its just a very short Guide, but I hope you all enjoy playing here this way! Im really glad if you leave me a comment or vote :D
Have a nice day and good luck!