I'd suggest using an ice type or dragon type Pokemon since they're super effective against dragon itself. Carry plenty of hyper/max potions and revives in case you're in trouble. For a dragon type Pokemon, get Fraxure by evolving it from Axew, it should know dragon claw which will effect the Pokemon for sure. An ice type Pokemon could be Vanillite or Cubchoo which will evolve into powerful ice types with effective moves.
Oh, and I'd also make sure most of your Pokemon are past level 39 if you challenge Drayden. Hope this helps! The last answer wasn't really easy to do. So.. enjoy!
8th gym leader
You either go and beat the 8th gym leader Geovanni in Viridian or go to with bill to the island and train plus do him some favours
beat the 8th gym and then go up and there is a person from hoen and also gym leader will give it to you
You must go to the Pokemon Gym. Beat the gym leader and he awards you with the 8th gym badge
Giovanni
8th gym leader
you beat the gym leader
The 8th gym leader is Drayden, who uses Dragon-type Pokemon. You face him in Opelucid City.
in the fortree city
you go to blackthorn city to fight the 8th gym leader
You have to beat the gym leader to gain acess to the Dragon Den. (the 8th gym leader,the on in the town)
Go to Evergrande City to beat the Elite Four
The only way to get a gym badge is to challenge the corresponding gym leader and win.
In the original Pokemon Silver you had to beat the 8th gym leader, Claire, then she allowed you to pass.
You either go and beat the 8th gym leader Geovanni in Viridian or go to with bill to the island and train plus do him some favours
you must beat the 8th gym leader and she will grant you passage to dragons den
Since Clair (the gym leader) is a dragon type, I suggest using a powerful ice type.