I am not a pro player and am not a rengar expert this is my interpretation of the champion and just some general tips, guidelines and builds to adapt upon. Thank you and happy hunting

Your playstyle will reflect on your understanding of the champion, the comp and your setup(Runes/Build).Not to overcomplicate things, but this champion is very difficult to grasp. the trade off is when u do manage learn how to utilize his kit you have no boundaries the skill cap is very high in my experience.

Rengars base Q gives bonus damage to your autos and can be used as an auto reset
(this can be cast pre/mid jump to apply to your leap auto)

Rengars base W stores dmage as grey health when cast you heal for the grey health and deal AOE magic dmg to nearby targets.(learning when and how to use the w to survive burst and sustain is curtail to winning your fights)

~Rengars passive allows him to leap a fair distance from bushes auto attacking the target. (At 0 stacks this will grant you 1 stack) (stacks last 8 seconds without attacking)

The key to Rengar is stack management and timing. you have 4 stacks instead of manna or energy. You are granted stacks by using abilities (1 Ability = 1 Stack). at 4 stacks you gain a recast on 1 of your three abilities (depending on your choice). All 4 stack albites grant you move speed with its unique trait.

-The 4 stack Q grants you increased damage on the q cast and temporally gives an attack speed boost (Bread and butter Dmg)

-The 4 stack W grants a cleanse to all crowd control with the exception of displacements and knock-ups. (Great against burst dmg and CC Denial as well as taking objectives to keep you as healthy as possible)

-The 4 stack E will cast a skill shot bola snaring a target for a short period of time
(Use for locking down and enemy fleeing or as an escape tool)

Learning when and what 4 stack to use when comboing comes down to your understanding of the situation and what is needed to give you the advantage in the scenario.

Your ability to use brush to your advantage and using stacks for what the situation calls for is what makes Rengar have outplay potential fighting near bushes allows you to always have an advantage over your opponent. it is his source of mobility and stack management.

In my 'opinion' full clearing is the most optimal if you can get a leash. it doesn't matter what side you start. there are many tricks to improving your clear. here are a few ive seen and implemented.

~Prioritize 4 stack q for single target camps & 4 stack w AOE for multi target camps

~Using the blast cone that spawns near both buffs will grant you 2 stacks if you q it from a bush. this will slightly increase your clear speed giving you a 4 stack q sooner. (Hit blast cone at 1:25 for best timing.)

(Red start)
-Place a ward or pink ward in the Krugs brush to give you sight of the Krugs camp. when you finish your red use the bush next to the buff to leap the wall)
this is a few seconds faster then walking around.

-Kite the smallest Krugs to raptors so your stacks do not decay
once you have 1 raptor left kite it to wolves and throw your e at the wolves to ensure your stacks don't decay.

-Draw the wolves as close to the blue buff wall without dropping agro then throw your e at the blue. (this allows you to do wolves and blue at the same time. the positioning is difficult but it speeds up your clear juristically combined with the next step)

- After killing Wolves kite your Blue to Gromp and take both at the same time
(doing blue and wolves then blue to Gromp in succession shaves large amount of time off your clear. But be weary of invades at this stage you will be lower hp and vulnerable to being cheesed)

- Use 4 stack e to break the scuttle shield. (the snare cc applies the debuff to break its shield.)

You can reverse this clear in a slightly altered fashion but id recommend red start I think its somewhat faster but I might just be more comfortable with it over blue start.