Help a trash player out.

So like...okay. I realize this has prolly been asked a millions times and someone is gonna say just "git good", but i dont understand how i can get better at this game. I play jungle and support primarily and I feel like no matter what the other team just gets so far ahead i cant help enough.

I usually play: lee sin (m6), kha zix (m6), and sejuani. I feel like no matter what my team gets so behind due to some lane feeding that my ganks dont do enough. the other team gets a fed zed or yasuo or warwick and they are just unstoppable.

is there a secret? I am just wanting to improve so i can start ranked play.

thanks.