This guide is dedicated to the community of r/rengarmains. I expect that you already know at least the basics of Rengar, and I'll therefore keep this guide as short as possible and just give you some insight on what to do throughout the game.

If you want to know a little bit about my own experience, I've been maining Rengar since his release in s2, and then been otp him throughout s3, s4, s5, s6 and now s7.
I've been topping the diamond league many times, but unfortunately never made it into master tier.

Throughout the guide we'll be going over:

• Preperations - Aka summoner spells, runes and masteries
• Item builds
• Playstyle
• Early/mid/late game

Summoner spells

The type of summoner spell you'll be picking really depends on the matchup. I've given a small tip on what to pick against whom in the vs champion section.
There are 3 things I'd consider to be good summoner spells on Rengar.

Exhaust

Ignite

Teleport

These three are useful for Rengar top lane. As Rengar you are an uncontrollable snowball if you manage to get started rolling, but has a very hard time putting yourself back together if you fall behind. This is very Rengar goes untraditional and sometimes take ignite and exhaust to increase his dueling potential.
As a headliner, you want to pick your spells like this.

Exhaust: The enemy can outduel you and you need to reduce their damage output

Ignite: The enemy doesn't have any hard burst that can kill you,and you therefore want more damage, especially in the early game, to increase your kill potential and get your snowballing started.

Teleport: The enemy can roam better than you, so you want to be able to countergank them with teleport. If you need to be able to recover faster from being beaten in lane, teleport also helps you that way.
You can contribute to your team better by splitpushing, and then teleporting to them when they need your help. This will also allow you to contest dragon all the way from top lane.

Runes

If you haven't discovered by now, there's no "set" build path for Rengar and he can really adapt to many situations.
The basic loadout of runes I use are:

9x Lethality marks
9x Armor zeals
6x CDR glyps
3x Scaling CDR glyphs
3x AD Quins

With the CDR glyphs you'll reach 10% CDR, and you'll therefore get 40% CDR with Black Cleaver and Ghostblade.

Masteries

Thunderlord's Decree, Precision and Bounty Hunter is all that matters here.
If you wanna be fancy you can pick up Stormraider's Surge instead, but it'll cost you burst damage.

As the prey evolves you must adapt.

What this means is that you will have to shift your build every now and then. Meta changes all the time, and you'll have to find new items and build paths to counter the new OP champions in play.
Fortunately for you, Rengar has the tools to adapt to almost any meta (yes, even after the rework).
The most commmon build path is the bruiser Rengar. The item build I have listed does allow for bruiser build, but preferably you should go for damage if you can get away with it.

Tanky top laners

Fighting tanks or juggernauts will put assassin Rengar in a bad position. Their bulkyness and cc will prevent you from snowballing, and you'll therefore have to focus on a more bruiser-ish build with armor pen (aka lethality) in it.
Always start out with a Black Cleaver against these guys, and then you can either work towards lethality if you are doing good, or take a more "defensive" item like Death's Dance to give you some lane sustain and reduce damage taken. The CDR also compensates for Ghostblade.
Pick up Last Whisper early here.
I do not recommend going Deadman's Plate/Spirit Visage as a second item.

Fighter top laners

These are guys like Fiora, Irelia, Tryndamere etc.
Start out with Black Cleaver again, as this will allow you to stay toe-to-toe with them, especially if you got 2 Doran's to help you boost your health. You do not need to think so much of survivability against these guys, as you'll do better off if you get lethality over anything else after Black Cleaver.
If one of them starts to build an early armor item, like Irelia going Randuin's Omen, then pick up a Last Whisper to penetrate their armor.

Squishy top laners

These are guys like Gangplank, Yasuo and any other carry type champion.
These guys can easily be 1 shot if you're ahead, and thus you should try to get damage early on if you aren't being beaten hard.
Pick up Ghostblade early and then take Black Cleaver second.

As a Rengar top laner, you depend entirely on your ability to snowball yourself during the laning phase. You got the advantage that Rengar is an extremely powerful champion to face, but like most top laners, you lack a reliable escape mechanic.
As a "feast or famine" champion you'll have to secure yourself the early game, otherwise you'll have a really hard time recovering. Rengar is amongst the strongest early game champions however.
Abuse the bushes as much as you can, and if your opponent overextends and walks too close, don't hesitate to jump on them and punish them. If they retaliate you can retreat with an empowered W, or press on with your other empowered abilities.

Abuse the fact that Rengar can beat any champion at level 1, and also take advantage of the fact that most people do not want to miss their very first lane as it's crucial to their early game and to get level 2.
You can quickly pounch on them to land a quick Q before going away again, and then whittle them down until you finally surprise them with an empowered Q in their face. This will most of the times either score you a kill, or make the enemy use their flash.

Because if you decide to pick up either ignite or exhaust though. They might boost your kill potential, but if the enemy has taken teleport they'll be able to get back into lane rather quickly after you kill them or send them home. If you get too low on health, you'll have to push the lane quickly and recall if you want to keep your lead.

Don't forget the jungler

Rengar does not have a "real" escape mechanic, and you will therefore have to watch out for the enemy jungler. You will most likely play aggressively, and the enemy jungler will take notice of this and try to gank you. It's therefore of most importancy that you get control wards. Place them well, and don't allow yourself to get snuck up upon. That's your job.

Once you get your ultimate

You'll have to use your advantage to do more than just kill your lane opponent over and over however.
With the rework, Rengar unfortunately needs to get kills on other people than just his own lane. This is the disadvantage that jungle Rengar does not feel (but is heavily nerfed with patch 7.5). Once you acquire your ultimate, you should look to push your lane and then quickly decide a lane to gank. Prefer to gank bot lane as there's a double chance to score a trophy, or even get 2 of them. If mid lane is more of a guaranteed gank however, then prioritise that instead.
If you have someone mid lane with high cc, like Lissandra, then tell them to gank bot lane with you so you can get your trophies.

Teamfights

With the rework Rengar can unfortunately not just walk through his enemies, and they'll be knowing that he's coming way before you get a chance to set anything up. As Rengar however, you do not have to charge through the front, but you can instead circle around the enemy team to flank their carries. Do not worry about your team though, you got more than enough movement speed to get around quickly, and then have the damage to eliminate any backline threat.
It is not wrong to target one of their front line fighters, provided they are not a beefy juggernaut or something.
The only thing you have to watch out for however, is the enemy support champion. No matter how fed you are, if you get silenced by Soraka, cc'd by Janna, pulverized by Alistar, polymorphed by Lulu or anything like that, you won't make the kill and you'll have to start running. You need to consider yourself whether you can make the kill in time, or if it's better to focus on somebody else where you don't put yourself in so much danger.

!! Avoid full assassin Rengar when against a team with lots of peel !!

Remember your presence

Always remember that Rengar is a hunter, not a full on assassin. If that's what you wanted I suggest you try out Talon. You're capable of hunting down prey easily, but if you do not at least get some form of survivability, you'll get blown up faster than the enemies.
Your presence in team fights affects your enemies directly, even if you cannot feel immediately, it can heavily affect an opponent's skills and reaction time when under the effect of your ultimate. People know that Rengar is a large threat, and they will most likely always try to prepare for you, also mentally (if that makes sense).

Early game

• Play aggressively
• Try to get a lead so you can snowball
• Buy control wards!!!

Mid game

• Roam
• Dominate the objectives
• Fill up your trophies

Late game

• Kill the enemy carries
• Do pick off with your ult
• Watch carefully if one of them is farming alone in a side lane
• Split push if you have teleport

This was a small guide on how to play top Rengar according to me.
I apologise for any spelling mistakes I've made, it didn't exactly take a short amount of time to make this :)

Have a wonderful day.