In this guide I will try to explain you how to build and play pure ability power Evelyn. I have to warn you that playing as Evelyn especially if you have a good team can be easy from time to time but being a decent Evelyn player is really tough. Decision making and timing really makes a big difference between a normal Evelyn player and a pretty good one. It requires some experience in order to become a good Evelyn player.

Well you can select between variety of rune builds for Evelyn. You can get some decent hp to survive more early game (which is very important for Evelyn) and add some ap to it or you can go magic penetration. My favourite is attack speed and cooldown reduction. It may seem a bit odd but after a certain point half of evelyn's dmg comes from basic attacks(especially after you get Lichbane). You can change the percentage of attack speed and cooldown reduction according to your play style but that's basically what I use.

Masteries are just basic 9/0/21 build. You can also go for 22/0/8 but I prefer to get cooldowns and flash cooldown especially because it is very important for survivability. You can check what fits you best. My build is not a must but very efficient.

I like to start with a health potion and Doran's Ring as it gives some nice hp boost, ability power alongside with some nice mana regen. Until level 5-6 if you do not burn your mana too much you would not have a problem with going out of mana. You can also start with Amplying Tome in order to save some money as when you get Doran's Ring you have to collect 1235g to get Mejai's Soulstealer but Tome gives you no hp and no mana regen so I without an exception always get the ring first. If you do not have to return because of healt issues try to collect the money required for Soulstealer before you recall as it is a VERY important item for Evelyn. I always get it before the boots in order not to miss any stack. After that boots are really important too. I prefer Boots of Mobility because it allows me to wander quickly around the map and allow me to gank easily. Sorcerer's Boots are not a bad option too but Mobility is more efficient. After those I go for sheen. With hate spike spam, sheen (and especially Lichbane after) becomes extremely efficient. After you get sheen if you do not have problems with surviving I suggest you to comeplete Lichbane but if you are having trouble about surviving then I suggest you just to take Giant's Belt then complete Lichbane. After you upgrade your sheen to Lichbane next item is Rylai's Crystal Scepter. It is important to keep your targets in your reach and this item is the best way to provide it. Another important item is Banksy's Deathcap (this is the new item that gives 135 ap and increases your ap by 30%. was not on the list thats why I put Zhonya's Ring to the list) Last item is actually up to you. You can go for Abyssal Scepter for more Magic Resistance or Void Staff for more dmg or something else according to what you need most (it changes from game to game).

Especially in early game as Evelyn does not have big dmg output ignite is a good way to make some extra dmg. In late game it has no big effect but if the other team has heal or healer or mundo it can have a great effect when nuking a target or when it is not possible for you to catch a target with low hp. Flash is an ability that is core to my play style. As Evelyn can die pretty fast using flash and ulti can be a great way to escape otherwise certain death situations. Also if you get boots of mobility and use your ulti with flash makes it almost impossible for any target to escape from you.

Alternatives: Teleport can be a nice way to travel around map in order to gank easily. Ghost can be an option too but you have your ulti so I think it can also be a waste. Exhaust can also be used to escape or disable the opponent so it also is not a bad option.

I start with Shadow Walk and once I hit level 2 I get Ravage. At level 3 I get hate spike because after you use ravage your basic attacks dont hit much. Hate spike is a nice dmg boost. Then get another ravage and at 5 I either go for ravage again or shadow walk. Depends on my mood tbh :P If your lane friend has some decent dmg stunning for longer can be better but ofc ravage is a nice boost too. Totally up to you and what you need. At 6 ulti then 7 hate spike again. After that point if the other team easy to kill ravage is better but if combats are a bit longer even 1v1 then hate spike gives you more dmg. Until 11 give one more point to shadow walk then distribute others between hate spike and ravage. Between 11-16 again 1 point to shadow walk and same thing again. At level 16 u basically should have a balance between your skills like 3/4/4 give or take 1 didnt do the exact math.

Up to this point it was easy stuff about what to get as spells and items. Now from now on is the tricky part. I have played countless times with Evelyn can say (no bragging) that I am a decent Evelyn player but you need to have 1) a good coordinating team 2) very good timing and decision making
After you get Soulstealer it is very important for you to survive. Especially after 8-9 stacks, if there is not a target(s) in other team that you can pretty fast kill 1 on 1, you cannot afford to die. 20 stacks of Soulstealer makes Evelyn a very different champion.

When you are laning with Evelyn it is important that you have a decent damage dealer with you. When your mana is full you can use ravage to harrass your opponents. Make sure that they cannot recover that health fast or it would be a waste. Also make sure that you get some minion kills to get some money. Hate spike can be a good way as its cost is very low. If you have a stunner with you in the lane its generally very easy to get a kill once you are 3-4. It is best to talk about the strategy before you go in though. Basically your laning is about the champion you team up with. Also dont forget to check middle from time to time. Both middle laners may have low hp and helping your teammate can greatly change the game as he will be alone at mid once his opponent is dead. That will allow him to outlevel his opponent and give a great advantage to your team.

Firstly you need to be sure that the champion you are about to attack is not strong enough to kill you. You need to know if you can kill him for sure. That requires experience there is no easy way to express this knowledge. Once you start to learn Evelyn you know what you can or cannot do. An important point here before you engage 1v1 is to wait for target's certain abilities. like you can wait Kassadin to use his ulti right before engaging so he may not escape. As I said timing is important. Preferably at lower levels do not engage alone too much unless the target is low on hp or its a certain kill.

This probably is the hardest thing to learn as an Evelyn. This champion is not a team fighter. People may not know/understand that and may ping on you when you dont join the fights immediately but that should not concern you that much. Of course do not just sit back and watch the fights but Evelyn should be the last champion to engage. In team fights there has to be a focus target but sometimes your teammates may not arrange it so they divide their damage to more than one champion but there generally is a champion who gets some decent damage and tries to escape. That is when you enter the fight. You should quickly finish it off with ravage and always use your ulti before you enter a fight. Always. After you take that kill according to the balance of the fight you decide your next step. If your team has the advantage you can just rush in and spam your hate spike and ravage when it cools down. If your team is not winning the fight going away from the fight and stealthing again to look for another easy target is a good way. Yes people will say that you just go for low hp champions and stuff but without you they always escape and once you get those kills and become fed then there is no stopping Evelyn. So basically teamfights are not a very good option for Evelyn to engage unless you have a certain advantage. But as I said dont just sit back and watch. There has to be a way to involve yourself either by catching the low hp guy or stunning and rushing out to save a teammate. Again the best way to adapt yourself into team fights is through experience.

Evelyn with her ulti (and flash if you have it) is an excellent tower diver. People may forget about you and may recall at towers with low hp. Once you see such player you need to think before you engage. Firstly there shouldnt be anyone around who can disable you with stun, taunt etc. to save his teammate. And you need to be sure that you can get the kill really fast. Otherwise tower can finish you off while fighting. Basically make sure that you can finish of your target with one ravage and a hit or two. Also with some teammates towerdiving can be extremely effective with Evelyn.

One of Evelyn's most important quailties is to ability to scout effectively especially if you have boots of mobility. But before you start scouting ALWAYS check for oracle. It is so vital for Evelyn to know if the other team has oracle or not. Once you are sure that you are safe to go Evelyn can scout other team to prevent ganks and to create gank opportunities for her team. Evelyn can spot champions that farm alone in jungle and can create a good opportunity for the team to get a kill or if strong enough she can get the kill herself. Also while scouting you steal buffs from other team with a good timing and escape by using your ulti. Also you can effectively ward the map so that your team will always have the advantage even if you cannot scout at the moment. Also while scouting if you see that team members of the other team are seperated and they are not defending a lane after you get Lichbane you can down turrets pretty quickly.
One last tip about backdooring. Well some people may call you "noob" or "you can only win like that" but still thats a nice way to use Evelyn. If the other team has an inhi without a tower defending it you can go get it but make sure that other team's minions are around the inhi so that you can use hate spike and can get Lich bane buff consistently to down the inhi very fast and also use your ulti too

Pros:
Crazy dmg output
Fast efficient scouting.
Ganker
No mana problems (especially late game blue buff recommended though)
Can escape quickly

Cons:
Once disabled almost certain death
VERY item dependent
Because of soulstealer very kill/assist dependent