Quinn is interesting sort of combo Champ. She has some parts of Vayne/Ashe and parts of Nidalee. Oddly she relies solely on AD to be successful. First and foremost speed is her greatest asset. Early speed and a bit of accruacy (Q attack is directional only down side) will get you some early harass and kill hits. Don't be afraid to wait for someone to initiate as her burst damage is considerable early on when properly setup.

Stick with MR and attack speed runes when possible. Fiddlesticks tends to shred her at all levels of play when not acutely aware of what is going on. Armor helps some but, generally you want to be away from the main fighting and using your range and speed to get quick kills.

The closest build would be a good Vayne build, heavy on attack speed/dmg and some cool downs would help too. 21/9/0 or 21/6/3 for bit of speed boost. Stick with what works best for melee it will help greatly early on especially.

SPEED, SPEED, SPEED. Try to maximize your speed early when your speed gets up enough dmg will come with it. You can easily gank and stay at a respectable range with attack speed and timing. I recommend boots to start or Doran's blade as both are invaluable early on. Get Zeal as soon as cash permits, from there get berserker's boots and work toward getting Phantom. From there build to suit but, I prefer to stick with what's most reliable, The BloodThirster and Warmog's.

Try to maximize your E attack early as possible 3/1/2 for the first 3 levels. From there follow E attack out quickly as it will be your bread and butter late game and in a pinch getting out of harms way and getting a quick got ya last chunk helps too. W attack is semi useful when you're pushing to help avoid any indirect gank attempts or lurking Champs waiting in the wings.. The best part is they generally won't know you've spotted them which is good for Q/E attack combo.

Stick with something that's going to cover you in a pinch as Flash and Barrier will do. Heal and teleport will help and work nicely when you're needing to move in an hurry.

Pros, Evil in mid/late game harassing and ganking, if done correctly near impossible to take down solo with the range advantage. Cons, easily countered attack combo due to nature of the Q attack quirkyness and reliance on accuracy. DOT and direct contact ranged do her in as her health isn't great at any level. Always try to keep range between you and them. Melee will eat you up quickly.

Solid work with a heavy melee/tanky partner. One with great CC or an isolation attack like Volibear work well with her. Avoid ranged counterparts when possible as you have no cover when getting a push going.

She farms moderatly early on speed will increase her farm rate dramatically as will following Valor's queues. Use the targeting to isolate sure fire damage boosts and get quick cash around 3-4 lvl range. Later on you will get much faster as cashing in on lane and some quick ganks will get you up in a hurry. Don't push the ganks focus on cash from mobs to risky with her squishyness to risk it.

An intersting mix of 3 different champions make a formidable quick strike and hit and run AD Carry or early AD push. Be mindful of her low health and you can initiate if you've got a handle on her Q/E combo to start with. When you have couple Bloods/Phantom blade under your belt init will be much smoother and quicker.