Help w/ Top Lane

Hey, so recently I've taken up top lane for my upcoming tourney. As an Evelynn main I don't have much experience up there and need some pointers. One thing I noticed that I suck at EXTREMELY is last hitting minions versus a ranged champion. I don't understand how you can farm when they harass you down every time you want to last hit, and its not like you can harass them back since they have the advantage. I was thinking of taking the Bandit Mastery, but for the tanks I'm playing you usually go 12/0/18.... I don't know what would be a better buy either, Doran's Shield or Corruption potion.... I think it would be Shield since you can walk in for CS, use that passive than walk out. Below is a list of the champions I play top, and some I'm learning. If you have any tips about CSing and trading with the enemy I'd appreciate it. I also am trying to learn Gnar to avoid not being melee lol.

Poppy Mastery 6 (I find her easy to Cs with her since her passive, but its not always up to CS with versus ranged) Maokai (Have a few matches on him, I use mana too quickly, and dont know how to trade or when to trade) Gnar (watching a lot of tutorials) Lissandra Mastery 5(same as quinn minus the roam) Quinn Mastery 7 (pretty good with her, especially roaming mid too) Irelia/Fiora (I can do really good with both, but need to work on when its a good time to all in.... level six for both? and both are mastery 5)

Thanks for reading, please leave tips and some advice ty