I need Evelynn Tips please

Evelynn needs to avoid long matches, as she is useless on late game. When picking eve, you are assuming that you will snowball at the early or mid game.
Don't panic if you don't get any kills, you can still full clear thousand of times and get ahead on xp and gold, she is good at clearing. Basically, what you need to do is powerfarm until level 6 and then gank any lanes with CC for setup, like leona on bot or renekton on top.