Striaton City Gym

Gym Leader: Cilan, Cress and Chili
Type: Multi
Prize: Trio Badge, TM83 Work Up

506
Lillipup @ Level 12
- Bite
- Work Up
- Odor Sleuth
- Helping Hand
Pansage Pansear Panpour
Pansear/Pansage/Panpour @ Level 14
- Incinerate / Vine Whip / Water Gum
- Fury Swipes
- Work Up
- Lick

These guys lead a weird gym. Depending on your starter, they change. If you pick Snivy, you'll face Chili, who has Pansear. If you picked Tepig, you'll have to battle Cress, who has Panpour. Finally, if you picked Oshawott, you'll face Cilan and his Pansage. Each trainer also has a Lillipup.

The best strategy to defeat Cilan, Cress and Chili is utilizing the gift Pokemon given to you in the Dreamyard. There's a young woman there willing to give you a Pokemon, depending on your starter. But instead of giving you the type-advantageous Pokemon, she'll give you the type-disadvantageous one. So if you picked Tepig, she'll give you a Pansage, which you can use against Cress's Panpour.

Basically, use that Pokemon to take them out.

Nacrene City Gym

Leader: Lenora
Type: Normal
Prize: Basic Badge, TM67 Retaliate

Herdier
Herdier @ Level 18
- Bite
- Take Down
- Retaliate
- Leer
Watchog
Watchog @ Level 20
- Hypnosis
- Leer
- Retaliate
- Crunch

A good Fighting-type Pokemon will come in handy here. I'd stay away from using Munna because of Watchog's Crunch. Due to poor type coverage, you can probably take them out with your starter. If that's not what you're looking for, try training a Timburr. They can be found near Pinwheel Forest.

Castellia City Gym

Leader: Burgh
Type: Bug
Prizes: Beetle Badge, TM76 Struggle Bug

Whirlipede
Whirlipede @ Level 21
- Struggle Bug
- Poison Tail
- Screech
- Pursuit
Dwebble
Dwebble @ Level 21
- Struggle Bug
- Smack Down
- Faint Attack
- Sand-attack
Leavanny
Leavanny @ Level 23
- Razor Leaf
- Struggle Bug
- String Shot
- Protect

All you need here is a really good Flying-type Pokemon. Tranquill and Swoobat will do the trick well, but watch out for Dwebble's Smack Down (or Faint Attack for Swoobat users.) Fire-types work well too, especially Special Fire. Pansage users will have fun in this gym.

Nimbasa City Gym

Leader: Elesa
Type: Electric
Prizes: Bolt Badge, TM72 Volt Switch

Emolga x2
Emolga @ Level 25
- Pursuit
- Volt Switch
- Aerial Ace
- Quick Attack
Zebstrika
Zebstrika @ Level 27
- Flame Charge
- Volt Switch
- Quick Attack
- Spark

A Ground-type is really useful in this gym, especially with a Rock-type move for her Emolgas. Excadrill is a perfect candidate and can Slash Emolga away and focus on Zebstrika. Watch out for his Flame Charge!

Driftveil City Gym

Leader: Clay
Type: Ground
Prizes: Quake Badge, TM78 Bulldoze

Krokorok
Krokorok @ Level 29
- Crunch
- Bulldoze
- Swagger
- Torment
Palpitoad
Palpitoad @ Level 29
- Bulldoze
- Muddy Water
- Aqua Ring
- Bubblebeam
Excadrill
Excadrill @ 31
- Slash
- Rock Slide
- Bulldoze
- Hone Claws

A Grass-type Pokemon is preferable and a Water-type will help you take out Clay's team. The Grass-type is primarily for Palpitoad, but will suffice for Krokorok and dent Excadrill. Water will be more effective on Excadrill but won't hurt Palpitoad much.

Mistralton City Gym

Leader: Skyla
Type: Flying
Prizes: Jet Badge, TM62 Acrobatics

Swoobat
Swoobat @ Level 33
- Heart Stamp
- Amnesia
- Acrobatics
- Assurance
Unfezant
Unfezant @ Level 33
- Quick Attack
- Air Slash
- Leer
- Razor Wind
Swanna
Swanna @ Level 35
- Bubblebeam
- Aerial Ace
- Air Slash
- Aqua Ring

The best choice for Skyla is an Electric-type. With Chargestone Cave nearby, the game begs for you to use a strong Electric-type like Galvantula or Eelectrik. Rock also works, but Swanna may prove difficult.

Icirrus City Gym

Leader: Brycen
Type: Ice
Prizes: Icicle Badge, TM79 Frost Breath

Vanillish
Vannilish @ Level 37
- Mirror Shot
- Frost Breath
- Acid Armor
- Astonish
Cryogonal
Cryogonal @ Level 37
- Rapid Spin
- Reflect
- Frost Breath
- Aurora Beam
Beartic
Beartic @ Level 39
- Slash
- Brine
- Swagger
- Icicle Crash

A Fighting-type is your best bet for Brycen. With Beartic's Brine, a slower Fire-type would have some trouble, as well as Rock-types. Rock-types may not even get pass Vanillish's Mirror Shot. Fighting-types have free roam over Brycen's team.

Opelucid City Gym

Leaders: Drayden (Black) / Iris (White)
Type: Dragon
Prizes: Legend Badge, TM82 Dragon Tail

Both teams are similar. However, Iris's Pokemon are all Females and Drayden's are all males. Iris's Druddigon also has Sheer Force instead of Rough Skin.

Fraxure
Fraxure @ Level 41
- Dragon Dance
- Dragon Rage
- Dragon Tail
- Assurance
Druddigon
Druddigon @ Level 41
- Chip Away
- Revenge
- Dragon Tail
- Night Slash
Haxorus
Haxorus @ Level 43
- Dragon Dance
- Slash
- Dragon Tail
- Assurance

Ice-types are key! Beartic's Icicle Crash should suffice, but Vanilluxe's great defence will also help too. It's all up to you.... Or you could use your own Haxorus or Druddigon on them.