It requires a lot of knowledge, a lot of very smart decisions that change game to game based on how your allies play, and a mentally healthy attitude right now. JG was a bit too strong end of last season and I started getting autofilled out. They nerfed it and it's all mine now. It is a bit tough though.
Anyway, as a JG main the absolute best piece of advice you'll ever get is DO NOT LISTEN TO ALLIES. If they ask you to do something ignore it, do what YOU think is best, because the second you bend to something you disagree with you will BOTH die. You know better and you need to accept that or youll fall while trying to appease your teammates.
So you have to have the mental to eat constant flame, and to ignore allies in order to do what you know is best. If you bend on either you're legit screwed.
The thing about JG is no matter where you land in ranks, you'll almost always have better game presence knowledge than whatever MMR you're at. The reason being knowledge if your largest tool to get where you get as JG. I've heard JG of all ranks say the same thing repeatedly, they started climbing when they learned to block out allies demands.
Also, learn to accept that your allies don't know where to place wards. It's not worth letting it get to you. Seriously, they all suck at warding except the support if you're lucky.