I'm not sure why Gengar is holding Toxic Orb if it's not tricking it, unless you predict that your opponent will be tricking an item to you? Even so, Black Sludge is better, since Toxic Orb is a useless item for Gengar.
Umbreon should have Foul Play instead of Sucker Punch. It's attack is woeful, so Foul Play is the best offensive move for it since it's calculated by your opponent's attack. It can even hit Dark and Fighting types pretty hard.
Rain Dance is a was of a turn on Magnezone unless Kingdra has Swift Swim.
Solarbeam is a waste on Arcanine since it needs 2 turns to take effect without Sunny Day/ Drought. Give it Crunch instead. I would suggest Close Combat, but that's an egg move. :/
As for your last team member, I would go for some team support, maybe Starmie or Forretress for a Rapid Spinner.
Starmie @ Leftovers
Ability: Natural Cure
EVs: 244 HP, 252 Speed, 12 Sp. Atk
Nature: Timid (is best, but we don't live in a dream world)
- Rapid Spin
Forretress @ Leftovers
EVs: 252 HP, 252 Def, 4 Sp. Def
- Rapid Spin
- Stealth Rock
- Volt Switch
If you feel you can do without team support, then here are some physical sweepers for you.
Dragonite @ Lumberry
EVs: 252 Atk, 252 Speed, 4 HP
Nature: Jolly/ Adamant
- Dragon Dance
- Outrage/ Dragon Claw
- Fire Punch
- Earthquake/ Roost/ Extremespeed
Breloom @ Focus Sash
EVs: 252 Atk, 252 Speed, 4 Hp
- Swords Dance
- Bullet Seed
- Mach Punch
Though Dragonite is adding another Dragon weakness to your team, it has Multiscale, which means it will survive the first hit and be able to set up one Dragon Dance. Other good physical sweepers would be Heracross, Scrafty or Huge Power Azumarill.