Evelynn can be very effective in game if used right. Early game you should use hit and run tactics. After Radabon's deathcap you can start nuking. Approach with Shadow walk, and come out of it by using ravage, use Hate spike and if they are still alive chase them by using Malice and Spite. By the time you catch them you Ravage should be ready to use and kill them which refreshed Malice and Spite. Rinse and Repeat. Have fun with insane kill to death ratios!

P.S- Hate spike has a cooldown of .75 secs or less so its is very effective in killing minions or just doing overall damage to champs.