Use Malamar and Excadrill. Trust.
Malamar can gravity, which will allow people to hit Levitate Hydreigon with tanky moves like Earthquake. You can also run a light screen to stall out special moves and for stalling. You can run taunt to stop Tailwind, Nasty Plot, and Dragon Dance. It's also a good idea to use fake tears, since you noobs are probably going to just randomly run some Special attacking Psychic think and get nuked without it. This is the number one support Pokemon, and it only takes effective damage from dark attacks.
Next, for a tanky attacker, and probably the best attacker out there, Excadrill. It resists dragon moves and is completely immune to a possible Poison Tera Blast. With mold breaker, it will ignore levitate. After a few Swords Dances, you should be able to spam Earthquake with Shell Bell. Do Tera Stellar, unless Hydreigon is revealed to have some kind of fire attack.
This is literally it. Even a noob like you can understand.
