Okay I noticed you were about to do Florina so I thought I should do the few gym leaders after.
Corey (with 2 super potions)
Skrelp, Level 26, Holding Focus Sash, Acid, Toxic Spikes, Water Pulse, Venom Drench (Adaptability)
Grimer, Level 27, Holding Black Sludge, Disable, Acid Spray, Mud Bomb, Acid Armor (Poison Touch)
Nidorina, Level 28, No item, Double kick, Venom Drench, Bite, Disable (Hustle)
Croagunk, Level 28, Holding Black Glasses, Sucker Punch, Drain Punch, Venoshock, Mud Bomb (Dry Skin)
Skuntank, Level 28, No item, Pursuit, Incinerate, Smokescreen, Acid Spray (Aftermath)
Crobat, Level 30, No item, Venom Drench, Venoshock, Air cutter, Roost (Infiltrator)
Shelly (with 2 Ultra Potions)
Illumise, Level 32, Holding Damp Rock, Rain Dance, Struggle Bug, Dazzling Gleam, Confuse Ray (Prankster)
Masquerain, Level 31, Holding Silver Powder, Struggle Bug, Icy Wind, Energy Ball, Icy Wind (Intimidate)
Anorith, Level 32, Holding Muscle Band, Aqua Jet, Rapid Spin, Knock Off, Rock Slide (Swift Swim)
Wormadam, Level 32, No item, Struggle Bug, Mirror Shot, Psybeam, Giga Drain (Overcoat)
Yanmega, Level 33, No item, Struggle Bug, Giga Drain, Air Cutter, Ancient Power (Speed Boost)
Volbeat, Level 35, Holding Leftovers, Tail Glow, Moonlight, Struggle Bug, Dazzling Gleam (Prankster)