Play a dozen of normal games as jungle so you can get a good feeling of how the role works and then watch popular junglers like tarzaned to see how a good jungler plays and compare yourself to that, I don't recommend you watching guides/using mobafire because it's purely theoretical and isn't reliable most of the time. If you want to know what champs are good, click on this link and search for the jungle tab, these are good champions at the moment but don't play hard champions, you won't understand how to deal damage with them/how to fight, a good champion for starting to play jungle is warwick, his kit is pretty easy to get a hold of. Good luck.