How do you get to the second gym leaders gym on diamond?

Answer 1

The second gym leader resides in Eterna City. To get there, you need the first gym badge, and the rock smash HM.

Teach one of your Pokemon Rock Smash, and go north of Jubilee city. You will go through a few outside areas and a cave. Then you will get to Floaroma town.

There are a few things you need to do there involving Team Galactic and the Valley Windworks, but after that's done, you just keep going north.

Go north through another grassy part, and you'll get to the Eterna Forest. There you will team up with an NPC with a chansey. She will heal your Pokemon (like a Pokemon center) after each battle. Note: the wild Pokemon will appear in 2's, like a double battle, and the trainers are positioned so that they will both jump you at once.

After going through the Eterna forest, just a short walk east and you're at Eterna City, home of the 2nd Gym leader, the user of grass-type Pokemon!

Hope this helps!

Answer 2

Go to Entera City. There's a Gym there and that is the 2nd Gym Leader.

Miles, (I finished Diamond)