The most important things of jungling are the ganks
you must try to get close and slow your enemie with your axe
then you can deal a lot of dmg, pick axe up, throw again
learn to smite is also important a good jungler can always smite drake or baron
also for steals, so when 15min in game, save smite (you got wriggle so mobs go fast down) for drake and baron

i start with vampiric, but can also go boots + 3 pot or cloth 5 pots
you also can take a gold item like hard of gold early,
than finish wriggle so fast you can, and get boots + maybe golditem
dan phage for more slow,
than go tanky tanky tanky
or summonerspel i take flash but with ghost it's also very good, go in a teamfight
pop your ulti was some CC's are on you, ghost en keep dealing dmg

i take normal, armor pen marks and quint, you can also take flat ad, cause you deal true dmg so
i get also some mr and you need armor seals for jungling

masteries are 21/9/0, full offense 21 and some hp and resistance for defense