How do you beat Clair?

A Lapras or a Pokemon from the Ice Path would be helpful, with their ice attacks. For Kingrda, I would use Ampharos to paralyze it and then keep attacking.

Use Pokemon who no ice moves for the dragonairs and thunder and grass types for kingdra

I reccoemend chancey or other decent Pokemon that know thunder moves. Also chancey can learn Fire blast,softboiled,ice beam and some other good moves plus it has over 400hp,and pus leftovers on it:D

You need some strong ice type Pokemon or dragon type Pokemon that know dragon type moves and have some paralyze heals

Try using a level 30-40 Remorade or Octillery equipped with an Ice Beam, or if not that, at least Aurora Beam. Dragon attacks are Supereffective against their own type, which means that a Gyarados's Twister will be nice, but Twister is weak, and some of Clair's Pokemon know Electric attacks, which are Ultraeffective against Gyarados, a Water-Flying Type. So just stick with Ice attacks, from a Lapras or Remorade or Octillery.

Use Pokemon who no ice moves for the dragonairs and thunder and grass types for kingdra and carry hp-ups

Wait...guys where I catch a ampharos or a remoraid or a octillery???

I evolved my mareep to get ampharos