Dorans for safety
Long Sword for extra cut down damage
Cull for Scaling
Q range: 1125 Units (Quinn's Q is 1050)
Gnar's Skill Max Order: Q → E → W
Level 1: Conduct Quinn Cheese level 1, and then instantly side step to juke his Q boomerang. After you side step it, auto him to consume the harrier proc & continue AAing afterwards to win the trade. Be careful not to get hit by his boomerang that returns back.
Level 2: Gnar will have W likely, so try not to get 3 tims in a row. This grants him extra damage and MS. Do short trades with blind, and then disengage after. He will bommerang behind minions, but if he misses make sure to engage on him for a trade.
Level 3-5: Gnar has jump, but you're not afraid of mini-Gnar in fights. Watch out for Gnar's bar; if it gets closer to red then Mega Gnar is coming, and he is scary only if he's in close range of you. When Mega Gnar comes, stand back and be careful till it runs out. To beat Mega Gnar, try vaulting him mid air if you have quick reflexes because your E cancels his jump. Be careful of vaulting too late because his W range is 550 (25 more than your E pushes you back) and so he can stun you during your vault if you time it incorrectly. If he gets his jump off, its probably better to side step his W when he lands.
Level 6: Avoid being near walls, his R radius is 475 units, which is short, so when you anticipate an engage from him, try to stand in the middle of the lane and you will be okay. You can out run Mega Gnar easily, but he can one shot you if he is able to stun you against the wall.
Matchup is Quinn favoured with experience.
I run fleet footwork against Gnar because you get sustain for his boomerangs, and the movespeed helps you to juke his Q, which is his main form of damage.
The essential part of the matchup is to dodge his boomerang with your W max + fleet, and when his boomerang is down, go in for a trade.
Mini Gnar is quite easy to beat, while Mega Gnar's damage is quite terrifying.
Don't go near walls when he is in Mega Gnar. Use your W passive marks to side step Mega Gnars rocks.
Quinn's vault CAN interrupt both of Gnar's jumps (mini and mega), so keep that in mind. :)
I like stormrazor to help kite mega gnar, and also run either gnar down.
If you dodge the boomerang, go for a big trade because he can't do much.
Be cautious of Gnar's W passive though.
3 AAs give extra dmg and grant him MS.
If you blind mini gnar, he can't retaliate much, so short combos after he's blinded will help you to win the lane.
Try to leave the trade before he can get those 3aas on you so that he doesn't get the proc bonus MS and damage.
Mega Gnar in lane is much easier to deal with because he can't boomerange to trade with you, and his Qs don't fly back towards him so he can't CS as well.
Also, Mega Gnar is much easier to Vault cancel his jump because the animation is much slower.
In Mega Gnar, be careful of Gnar's W because it can stun you, and the range is 550 (25 more than our vault range and auto range).
Ideally, save vault to retaliate AFTER Mega Gnar Ws you.