Norman has a Slakoth (Level 28), Vigoroth (Level 30), Slaking (Level 31) so I suggest you train a party of mainly Fighting type Pokemon to an average of about level 30 before you challenge Norman. Good luck!
Chat with our AI personalities
After you get the 4th badge go to petalburg city and enter the gym go through it then fight Norman for your 5th badge.
take the meteorite
after you beat flannery you go back to where your dads gym is and beat that gym hope it helped :p
I would say any fighting types.
The gym leader in the normal gym, your character's father will give it to you after you beat him.