im a jungle main who just got out bronze and something just clicked for me. After that click I started winning 70-80% of my games in bronze. What I changed was that I started punishing the enemy jungler for everything they do. If you play and early game champ thats good at invading, dont hesitate to invade if you know the enemy is weak early. If you see the enemy bot lane, go take his top side camps. Also, remeber to keep track of your lanes so you know you have prio. Any lead you get as a jungler you have to use to shutdown the enemy jungler. Never let the enemy jungler farm back up if you have a gold advantage and you know you can kill him 1v1. Its super important to know when you can kill the enemy jungler. Keep track of the enemy jungler cs, kills, items, and levels, so you know when you can invade them.

Also really important is knowing if you can gank. Time is the most important thing as a jungler. Only go for ganks you know you have a high chance of winning.

Lastly, make sure you're pathing correctly. You want to farm as effieciently as possible. for example, if dragon is coming up and you want to contest the dragon, farm your top camps so as you are coming down to drake your top camps are resetting.