i see the same mistakes every time i watch my friends jungle so here goes. not a pro, just a guy who mained jg for a long time.
- full clear first unless you have a REAL reason not to. invading level 2 with no prio is how you give the enemy a free kill
- track the enemy jungler. if he started red bot side hes probably top side around 3 min. ping it
- dont gank a lane where your laner is shoved under their tower. look at the wave before you walk in
- scuttle matters more than people think
- stop farming when theres a dragon fight in 20 sec
most silver games are lost because teh jungler is farming camps while a free objective dies. or the opposite, forcing ganks while 2 camps are up. pick a plan and commit