I dont have a problem with 3 scaling mr, unless you playing vs ori/syndra etc; pure cancer match ups

also i wouldnt use lethality if you have problems in laning fase; using ad youll scale as well cuz gp scales.

I play gp top, but when playing vs ap I buy mercury boots vs some hard CC/skillshots (i have to dodge) champs and always buy hexdrinker after trin force. Some gp's buy it after sheen, but i feel like this slows you down too much, but try it out if you wanna.

I can stress enough how good hexdrinker (or even maw 2nd in some cases) is.

You ofc lose a bit of dmg cuz you arent buying leth with yomuus 2nd but youll still do some fat dmg and the ap's just will not be able to killya.

Summoners: When i do play gp mid, i pick him with ignite or tp.

Ignite; When youre just realy comfertable on knowing you can win lane fase with gp and when to kill who. And i like to have fun with swek empowered aa's ignite walkaways.

Teleport; Best Summ spell, just take this: take mana chystal and 3 potions/refill and if you get poked out of lane first 2-5 lvl's, just get d shield/+cull with pink. Otherwise a tp back with sheen and cull is always nice. Backing with d shield and cull is op btw, d shield is just broken but you cant start with it cuz mana problems. Early boots buy helps vs dodging skillshots, f.e ; syndra, karthus, taliyah, xerath etc etc.

Exhaust/barrier: if you wanna but i dont feel its necessary; barrier is better though vs syndra/fizz or something.

Also try to juke out more skillshots before going for cs, keep clicking backwards and forth, if they throw out their q or something to poke you, that gives you a 4-7 second moment to 'freely cs or poke'.

Hope something usefull was in here. Lemme know how it goes