Could anyone help a newbie improve his showdown team?

Poliwrath @ Leftovers
Trait: Water Absorb
EVs: 252 HP / 252 Def / 4 Spd
Jolly Nature
- Hypnosis
- Ice Punch
- Waterfall
- Brick Break

Politoed @ Leftovers
Trait: Drizzle
EVs: 252 HP / 252 SAtk / 4 Spd
Modest Nature
- Hydro Pump
- Ice Beam
- Focus Blast
- Hidden Power [Grass]

Kabutops @ Lum Berry
Trait: Weak Armor
EVs: 4 HP / 252 Atk / 252 Spd
Adamant Nature
- Stone Edge
- Aqua Jet
- Swords Dance
- Superpower

Magnezone @ Choice Specs
Trait: Magnet Pull
EVs: 172 HP / 252 SAtk / 84 Spd
Modest Nature
- Volt Switch
- Hidden Power [Fire]
- Flash Cannon
- Thunder

Garchomp @ Choice Band
Trait: Rough Skin
EVs: 4 HP / 252 Atk / 252 Spd
Jolly Nature
- Outrage
- Earthquake
- Fire Fang
- Dragon Claw

Toxicroak @ Life Orb
Trait: Dry Skin
EVs: 28 HP / 252 Atk / 228 Spd
Jolly Nature
- Swords Dance
- Drain Punch
- Sucker Punch
- Ice Punch