Is it good for battles?

[Marcusube]

Alright what you can do is run a physically defensive Milotic with max HP and Defense (this would've been more ideal with a Bold Nature but Calm can work as well). Scald, Dragon Tail, Toxic and Recover for moves and run it with the Leftovers

Throw a mega stone on Gyarados and run Dragon Dance, Substitute/Earthquake, Crunch and Waterfall with max attack and speed

As for Politoed, you can be gimmicky and run a Life Orb Politoed with Hydro Pump/Scald, Ice Beam, Focus Blast and either Psychic or Toxic. If your Politoed happens to have Hidden Power Ice/Grass you can run that over Psychic for better coverage. Also try to grind Battle Maison for an Ability Capsule to switch Politoed's ability to Water Absorb

These are just sets I can suggest with what you have. If they had egg moves (eg Haze Milotic or Encore Politoed) then they could run those moves as well.