Not Updated For Current Season
You want the Greater Mark of Magic Penetration for your entire game as Evelynn, her entire damage output circulates around Magic Damage, so this shouldn't require an explanation. Magic Penetration will overshadow any kind of extra damage you can give her.
Now here's the one I expect the most raised eyebrows: Grabbing Greater Seal of Armor on Eve. Now before we start the blasting of poor me, remember this: The guide is one for jungling. With the masteries used for Evelynn, she is focused on reducing the incoming damage as much as possible. I experimented with it one game by throwing these on over from my Malphite build, it worked fantastic. Helps later in the game with the little percentage it shaves off from Physical DPS.
Greater Glyph of Scaling Ability Power for her late game, gives a nice scaling effect on our little wretch and could be swapped for flat, but I prefer scaling since I don't even start utilizing them against enemies until the scale is nearly at or overshadows the flat.
Greater Quintessence of Ability Power for your jungling efforts. Besides, 15 AP at level one? Then you get 15 AP with the scale after what, level 12 or so? I would take the 15 any day.
Here we have why I think this build works so well. We have the mastery in Plentify Bounty for Smite of course. In Defensive, I have maxed out the Magic Resist and Armor, then poured points into the Health Regen per Mana for her early level jungling when she needs all the Health Regeneration she can get. Not to mention that while Eve wanders around enemies, she can quickly restore health.
Putting points to reduce damage was a choice that I made since we are jungling and they help immensely with the high Health Renegeration and make Wolves extremely easy at Level 2-4. The Health increase is for that Early Jungle as well. The point into the Revive buff since if we are getting Revive, might as well get the mastery. Same reason we grab Plentify Bounty for Smite.
As for Utility, we get the increased Regeneration for my Health Regen focused early game, Experience increase for our Jungling efforts and Buff Duration masteries to polish it off nicely. We don't really need any of the final mastery buffs in this design, so don't worry about reallocating for them if your thinking about it, just don't.
We grab Smite because we are jungling. No further explanation needed.
In another guide, Revive is recommended. I tried the build and personally, I liked it. I just tweaked a lot of it towards my own view on Evelynn. However, using Revive was amazingly beneficial in every game with it, so it was retained. I have been ganked in jungle a few times, died to minions since this build comes close to dying early jungling, it's nice to have it as a back up. Later in the game, Revive is amazing to quickly return to the battle and aid your allies. Since you are Eve, you will be focused. Just die, revive, come back and get a double kill. I have done it on more than a few occasions.
Since we are Jungling and entirely focused on AP, we want that Hate Spike to dish out as much as possible. This spell, along with her attack speed, makes Guinsoo's Rageblade absolutely essential. With the new nerf to Hate Spike though, you will run out of mana more than anyone would like. This build compensates for that and I have proven it today. Getting it as high level as possible is your priority for all of your Jungling and ganking needs. Just remember, even with blue buff, you will find yourself still scraping the bottom of the pool for mana. This is okay.
Secondly, we are looking at Shadow Walk. With it's recent tweak, it now comes off cool down faster, but it's duration has been greatly reduced. You will need to spam this in team fights and keep your stuns up for not only yourself, but your allies. It is what makes this build really devastating by utilizing that still opponent and pounding him into the dirt. It's tweak actually made this build better, so I am happy.
Later game, Ravage is amazing. However, since we are jungling, it is postponed until you start needing it. I personally throw it off to the side, prioritizing her other skills. Once you get Madred's Bloodrazor, this skill shines like no other. It really makes that item worth every penny and the wait, since their both significantly large amounts.
Lastly, her ultimate Agony's Embrace is what makes Madred's Bloodrazor and her other items, worth it all. The huge increase to her attack burst allows for a quick pounding to a stunned target, utilizing her items to quickly pump out as much damage as humanly possible.
An essential item to have throughout the whole game, is your Philosopher's Stone. You have mana issues and will need as quick a gold generation during the progression of the game as you can get. To close the gap between your jungling and ganking, Boots of Mobility make a huge difference, this also includes reviving and returning to fights. Your core items are Madred's Bloodrazor and Guinsoo's Rageblade. They will get you everywhere with this build and really make Evelynn shine. Past that, you could really get whatever you want, because you should be winning. I seriously haven't built past those two items yet, look what happens when I try to:They surrendered the top game and the fourth game, I was just ganked in the jungle early on and died a few times doing my job initiating with stun. Still came back for the double kill once.
With this build, I have yet to lose. It took a few games to really solidify it, but the build works and has won me every game since I used it. I hope it can do the same for you and if it ever is used against me, I am going to cry.
Now go out there and enjoy playing That ***** Eve.