Outdoor Solar Lights

Meganium
-Solar Beam
-Light Screen
-Earthquake (TM)
-Iron Tail (TM)

Arcanine (Growlithe until lv50)
-Flamethrower
-Extreme Speed
-Flame Wheel
-Hyper Beam (TM)

Hitmonchan
-Fire Punch
-Ice Punch
-Thunder Punch
-Strength (HM)

Xatu
-Psychic
-Giga Drain (TM)
-Shadow Ball (TM)
Fly (HM)

Gyarados
-Hydro Pump
-Hyperbeam
-Twister
-Surf (HM)
~~~EVENTUALLY TURNED INTO…~~~
Dragonite
-Hyper Beam
-Outrage
-Steel Wing (TM)
Thunder (TM)

So far I have:
-Meganium
-Growlithe
-Tyrogue
-Gyarados

Please make suggestions to the pokemon and their moves as well as what the 6th slot should be.

Also, with any changes or comments you create, please give me an explanation

Thank you!

teach arcanine dragonbreath over flame wheel
teach meganium sunny day over light screen
teach dragonite thunderbolt over thunder, fly over steel wing
teach gyarados ice beam over twister, bite over hydro pump
teach hitmonchan submission over strength

get a golem (rather than xatu) with earthquake, flamethrower, rock slide, and explosion

although some switches seem stupid (like hydro pump to bite)- this will cover against all types, leaving you with no weaknesses.