"Prey on the weak and you will survive, prey on the strong and you will live."
―Rengar

That is exactly what you should do, rengar's awsome passive of jumping from bushes makes him the most fun champion to play and the most annoying to play against.
Nonetheless he can snow ball like a champ... you just need to know how to harass people.

This rune set offeres the best possible combination of att dmg armor and cdr (to get that 3q allmost consecutivly)

Pros
*harras like no other from bush
*take down **** load of hp from target (insta kill low hp targets)
*greate mobility
*greate attk speed
*good heal mech
*super good shield
*permanent tabs on where the enemy is (becouse of ulty), don't hesatate to use the 3rd rank of ulty (taking in considration that cd is somewere around 40 s)

Cons
*Squishi at fisrt (and to add to that most of his skills need to be performed up close and personal)
*need to know when to dive and when to stand back
*only real escape mecha is his ulty (so if they get vision wards or oracles your pride days are over)
*when doing well your targeted (this is a given in any game you play with this champ)

The only team work that works with this champ is pick off squisy targets and leave the big boys to your team mates! Proper placing and piking on the most easy to kill champs will enshure victory in team fights!

this buld gives the best dmg output, whil the survivability is stable and cdr helps with that seamingly "for ever" cool down in a fight.

Last hit creeps with q from bush (that way you build the ferocity up as well)
if laning ugainst long range try using boala strike as much as possible