Hi, I´m a Brazilian LOL player, started on Season 7, reached Gold on season 8.
Not the best Quinn player but not the worst either.

I mostly play support but like to jungle a lot as well.
Quinn is my favorite champion as her global presence and awesome chasing power makes her a lot off fun to play in any role.

I have been playing a lot of JG recently, and JG Quinn can be a Strong pick low elo cause most people underestimate her gank power early game, especially lvl 2. And how strong her mid game skirmishing power is. She can turn a 2x2 in a 2x3 and turn the fight over in seconds. That can lead to being feed and carrying games.
She is also a very strong dueler lvl 2 and can win most 1v1s on Scuttle Crab fights cause of Q blind and E repositioning power.

The basic early game pattern is Red - Scuttle Crab, Gank Mid. Warn you mid lanner not to push, you should walk up to the mid lane bush, Q if certain to hit, Ghost, AA, AA ,AA, that will Proc press the attack, now if your mid laner follow up the gank most people will flash at this moment, then you use your E, AA, if Q off cool-down Q again that will get First Blood most of the times, and help you or your mid laner start ahead.

Be carefull not to get tower agro on that play, since you may end up dieing or being too low on heath that the enemy jungle can just invade and kill you afterwards.

Depending on the enemy jungle I often go straight to bot or top do the other Scuttle Crab (if not done) and gank again, cause Quinn lvl 2 gank is so strong, it often catches people by surprise. And you might get another flash off.

Then you should focus on tracking enemy jungler using your W and map awareness to farm and counter jg as much as possible until lvl 6 where your gank becomes much better. Probably with your Bloodrazor already finished.

Its hard to solo drakes before Bloodrazor and boots so remember to ask bot lane for help if you see enemy jg is top side and bot lane has pressure to help secure drake.

Try to place a early game pink inside the Rift Herald pit, try to do it around 10 minute mark, when the enemy jungler ganks bot side and is not able to reach top fast enough, that can help you get early tower mid or Top probably and give you more map to roam around getting pick offs on the enemy team.

Learn to use W + E to wall hop using JG camps to avoid unwanted 1v1s in jungle or escape chases. Also makes your clear a little faster if you jump over a few walls when doing clears.

Mid game you should look to farm more get vision and gank less, and keep your eye out for skirmishes you can help your teammates arriving very fast and turn battles your side.

Team Fighting is not Good for Quinn try to kill ADC before the fight starts, but if they are grouping try to lure their attention to another part of the map like showing yourself on bot clear a single wave and quickly join your team or go top side looking or someone alone. You must be smarter then your enemy. Don't face them head on.
You want to come in and clear a fight, not get hard CCed and die because your so fast your team cant keep up and help.

Late game is Quinn fall off, since you should be looking for pick offs in side lanes or supports going too forward alone to ward. Map vision control is a must. if your team losses map pressure too early on the game, ex mid lanner loses turret too fast it becomes very hard to do Quinn's job on the game.

Always scout using W to avoid getting picked off yourself and focus on doing objectives drakes and baron.

Hope this guide is useful for someone who wants to try JG Quinn, specially against tanky comps where normal lethality Quinn fall off rather fast.

I´ll improve on the guide as I can, comments and questions are welcome.
I´ll try to add a gameplay video later on.