Not Updated For Current Season
The masteries shown here are not yet updated for the current season, the guide author needs to set up the new masteries. As such, they will be different than the masteries you see in-game.
With this build Evelynn is a DPS Carry, she can kill fast late game but may struggle early game. I've played Evelynn alot lately and found that this build works really well agaisnt any team. Killing tanks and any champ really easily. This build does not require you to farm alot therefore you can mainly focus on ganks early game.
Once the game starts you should buy boots and 2 health pots and a mana pot. You can substitute the mana pot for another health pot if you prefer. Depending on who you are laning agaisnt you will stay or gank alot. If you are laning with someone with low health like Ashe or other carries you should stay and kill them often. While if you are laning agaisnt a champion like Rammus I would prefer you to go gank another lane. When you first go back to your base you should buy items for your Wriggle's Lantern and finish your Boots of Mobility, though you may get whatever boots you want or are more suited for the other team you are versing.
Mid - Game
By now you should have boots and a Wriggle's Lantern and you should be starting with your Wits End. Though you may substitute wits end for a Sword of Divine if the other team has only 1 or 2 champions that have mana. By now you should also have atleast 25 to 60 minion kills. Now that team fights have started you should always target the carries never the tanks like usual kill off champions like Ashe or Malzahar and then work your way down to the tanks. When you are not in a team fight and you find someone alone you can always 1v1 them but I only suggest this if you know you can kill them. Also during team fights you should never go in until your team has or else they will kill you first. Nearing the 30 to 40 minutes mark you should have started or finished your Madred's Bloodrazor.
Now that you have your Madred's Bloodrazor you can now solo almost anyone on their team that has low amounts of health (~2,000 or less) or is not fed. You can now build whichever item will help you the most if they are stacking armor you should build a Black Cleaver why not a Last Whisper well because I prefer to have more attack speed rather then armor penetration due to the Madred's Bloodrazor and the Wits End. After you have all of your build done farm 2,000 gold and sell your Wriggle's Lantern for another Bloodthirster.
Runes and Masteries
Masteries- For Masteries I prefer 21/0/9 though you can also have 23/0/7. Either way works except I prefer 21/0/9 because you don't actually crit much so its a waste of points. You can also change greed out for another mastery but if you can't farm much it gives you an extra 300 to 600 gold per a game.
Runes- For Marks you can go with armor penetration of magic penetration marks armor pen is self explanatory but magic penetration helps your spells that you constantly cast also because I only have magic penetration marks. For quintences you should have 3 health quints because they are good for any champion and because it just helps early game so you don't need to get a dorans item.
How to Play Evelynn
During laning phase you should not constantly stay stealthed but you should farm and then stealth and harrass at level two with your ravage A.K.A. e. I prefer not to gank but if you have played Evelynn for along time and you know how to then you should. Once you get your Wits End it is possible you can 1v1 alot of mages but don't solo anyone with tons and tons of crowd control until after you have gotten a bloodthirster or black cleaver. Early game you will probably be getting alot of assists I hated that but late game it makes up for it. When you initiate someone stun them and then e and rapidally tap your q while you auto atk. If they are running away don't forget to ghost and ult. Don't keep chasing stealth and stun them again while chasing. Then if you are winning and at their nexus be sure to go stealth and walk into the fountain turret because it can sense you and I just find it fun.
Hope you like my build, this is the first one I've ever made and I've done so well with Evelynn that I wanted to share this build with all of you. Heres a sample of how I've done with Evelynn.