Hello everyone and welcome to my guide on Rengar, The Pridestalker. Here are His stats.

Stats

HEALTH: 586.3(+90/lvl)
Health Regen: 4.27(0.4/lvl)/minute
Resource: Ferocity; Max Stack Count: 5
Range: Melee
Attack Damage: 60.04(+3/lvl)
Attack Speed: 0.679(+2.85%/lvl)
Armor: 25.88(+3.5/lvl); Magic Resist: 32.1(+1.25/lvl)
Base Movement Speed: 345

The Runes for Rengar shouldn't be strictly what I suggest the reason I use these Runes is because they are what I find the most success with. Additionally you can switch out the CDR Glyphs for Magic Resist if needed but the CDR is reccommended Because you have to get 40% CDR ASAP.

These are just my standard aggressive Top Lane/AD Bruiser masteries and they seem to work well with both Rengar and Renekton.(spoiler expect a Renekton guide)

Unseen Predator

UNSEEN PREDATOR: While in brush or in stealth, Rengar gains bonus attack range and his basic attacks cause him to dash to his target. This bonus lasts for 0.5 seconds upon exiting brush or stealth. Unseen Predator occurs regardless of whether or not his target has Sight icon sight of him.

Savagery

ACTIVE: Rengar's next basic attack within 3 seconds deals bonus physical damage.
BONUS PHYSICAL DAMAGE: 30 / 60 / 90 / 120 / 150 (+ 0 / 5 / 10 / 15 / 20% AD)
EMPOWERED SAVAGERY: Savagery's bonus physical damage is increased to「 30 - 240 」(+ 50% AD), and applying it grants Rengar「 47 + (3 × Rengar's level)% 」bonus attack speed and 10% AD bonus attack damage for 5 seconds.
Savagery resets Rengar's autoattack timer.

Battle Roar

ACTIVE: Rengar lets out a battle roar, dealing magic damage to nearby enemies and gaining bonus armor and magic resistance for 4 seconds, increased by 50% for each affected enemy champion or large monster.
MAGIC DAMAGE: 50 / 80 / 110 / 140 / 170 (+ 80% AP)
「 BONUS RESISTANCES: 10 / 15 / 20 / 25 / 30 」
Empowered Battle Roar.png EMPOWERED BATTLE ROAR: Battle Roar's base magic damage is modified to「 40 - 250 」and using it heals Rengar for「 8 + (4 × Rengar's level) 」, increased by「 6.25% per 1% of his missing health 」, up to a maximum of「 50 + (25 × Rengar's level) 」healing.
Battle Roar and Empowered Battle Roar's bonus resistances do not stack with each other.

Bola Strike

ACTIVE: Rengar throws a bola in the target direction, dealing physical damage to the first enemy hit and Slow icon slowing them for an amount that decays over 2.5 seconds.
PHYSICAL DAMAGE: 50 / 100 / 150 / 200 / 250 (+ 70% Bonus AD)
SLOW: 60 / 65 / 70 / 75 / 80%
Empowered Bola Strike.png EMPOWERED BOLA STRIKE: Bola Strike's base physical damage is increased to「 50 - 340 」and using it Root icon roots its target for 1.75 seconds.

Thrill of the Hunt

Thrill of the Hunt RANGE: 1250 COOLDOWN: 150 / 110 / 70
Thrill of the Hunt
ACTIVE: Rengar activates his predatory instincts, gaining stealth after 1 second of not taking damage or 3 seconds, and True Sight icon true sight of all nearby enemy champions for 7 / 12 seconds or until Rengar damages an enemy with one of his abilities or basic attacks.
VISION RADIUS: 2000 / 3000 / 4000
While stealthed, Rengar gains 15% / 30% bonus movement speed while moving toward a nearby enemy champion. Enemies are made aware of Rengar's presence if he is nearby.
Upon exiting stealth, Rengar gains bonus movement speed and generates 5 Ferocity over the next 5 seconds.
BONUS MOVEMENT SPEED: 25 / 35 / 45%

The summoner spells you can take as Rengar top lane are Teleport/Flash; Teleport/Ignite; Flash/Ignite; Teleport/Exhaust; and Flash/Exhaust. Which ever one you choose should be dependent on match-up.

Pros

1. Reliable early game damage
2. Snowballs incredibly hard
3. Extremely effective roam post 6
4. Insane mid to late game burst damage
5. Can lock on and remove backline for teamfights
6. Punishes bad positioning harshly

Cons

1. Ineffective roams pre 6
2. Easy to counter with pink wards
3. Relies on ultimate for kill potential
4. Can be useless if he doesn't get the lead he needs
5. Item reliant
6. Relies heavily on a snowball

FEROCITY

Ferocity is a mechanic unique to Rengar. Being able to micromanage this resource can make or break a Rengar player. You build up Ferocity by using abilities to a maximum of 5 stacks. At 5 stacks your next basic ability becomes empowered. Essentially giving these abilities bonus effects. Such as: Increased damage and attack speed on SAVAGERY, Increased Armor, Magic Resist, and a Heal on his BATTLE ROAR, and Making his BOLA STRIKE snare the target rather than slow them.

My inspiration for this guide is the challenger rengar stream Dekar173 here is a link:
Dekar173