I need Evelynn Tips please

Does anyone that is a good player of Evelynn got some tips for me ? I really beg u guys because I love the champion and the idea behind Evelynn. I play her jungle but in late game I become kinda useless... any tips for improvment please?

I play her jungle but in late game I become kinda useless

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.

set up strong vision control around objectives and in the jungle and be patient. use it to create advantageous positions for you, where you look for flanks on big teamfights.

Get a coach or just watch tutorials and apply them in ur games