This build may not be like some you're used to see. This is designed for those who want to roam early in the game while getting quick and easy kills later. Note that this guide is not perfect either and might not work in every single situation.

For marks I take Greater Mark of hybrid penetration not only because your skills are hybrid (Q doing magic damage while E does physical damage), but also because most of your DPS will come from your basic attacks. Combining this with the Sheen procs will help you do maximum damage.

For Seals I get Greater Seal of Armor and for Glyphs Greater Glyph of Magic Resist. Knowing there's not much hp in this build, you'll be ult dependant, meaning your Agony's Embrace's shield will be the healt you could've built in exchange of damage. The overall resist is here to make sure that shield won't decrease too fast.

Lastly, I take Greater Quintessence of Movement Speed to get 450~ movement speed with the help of the Mobility Boots helping you keep up with ennemies you're pursuing. Add this with the Trinity Force and you get about 480~ movement speed giving you a lot of fluidity to play with the border of your passive and escape any difficult situations, either you got a kill or not.

Getting the Hextech Revolver early is essential for it is your only source of sustain. Combined with the mana regen that comes with Eve's passive, Shadow Walk, you should be able to stay longer in lane. Mobility Boots will help you through out the game but especially early since you'll able to gank other lanes easily. I suggest getting the Alacrity enchantement, since 02/28/2014 patch nerfed the Mobility Boots pretty badly for our Evelynn.

Hextech Gunblade is used to combine the spell vamp with the life steal, wich means you'll have to use your basic attacks with your spells in order to do maximum damage (poke with your Hate Spike is still possible but not spamable). You could start with the Trinity Force instead but by doing so, you're giving up on your life steal to get the advantages of the other item (Health, Critical hit, movement speed and Sheen's bonus damage).

Abyssal Mask and Atma's Impaler are here to give you resist as well as damage, wich will help you take down your target quicker, for exemple, with the magic resist reduction debuff of the abyssal. Guinsoo's Rageblade will help you survive hard encounters even when low on hp, while Guardian Angel (if you choose to buy it) will help you take down one of the ennemies and damage the others while still coming back to life right after to finish the job.

When playing with this Evelynn, you'll be looking for quick and easy kills, like ADCs or squishy APCs wandering alone or even gank lanes that are easy to take down with the help of your allies.

Always begin the fight with Ravage. It does a lot of damage to the target who will think twice before fighting back that much power. If the ennemy decide to counter attack, Ravage's attack speed should win the trade if you don't get the kill.

When laning, play as defensive as you can. You might be able to score some easy kills by level 3 or 4 but try waiting for your passive's activation before rushing to your opponents, the element of surprise might destabilize them, giving you the advantage. If your ennemy seems too hard to beat, wait until lvl 6, then start ganking, assists or kills might give you the advantage you needed.

Before the start of a team fight, get behind the ennemy team by playing wisely with your passive's range, the Mobility Boots should help avoid ennemy detection if they end up falling back. At the begining of the fight, look for the squishy ennemies you want to take down, with enough damage you should be able to eliminate the target and escape with your refreshed Dark Frenzy. Using your ult on most (if not all) your opponent might, more often than not, be essential.

Take advantage of your movement speed and passive to juke ennemies pursuing you. Waiting for your passive to come up and playing with bushes might help you escape the most desesperate situations. When in a bad position, try to eliminate one of the ennemies to escape with Dark Frenzy and the Trinity Force's passive.

Pros

-Taking down alone targets.
-Gives you the advantage on some skill-shot/burst-only champs.
( Cassiopeia, Gragas, Lux, etc.)
-You'll be able to run away/juke from almost any situations.

Cons

-Hard early, you may have to play extremely defensive and wait for your jungler.
-Pretty weak against non-skill shot champs or those who can deny you when you rush.
( Annie, Ryze, Syndra, etc.).
-Pretty squishy early game.