For fairly good XP, I’d suggest fighting either in the grass just north of Olivine or outside of the Safari Zone and killing Wild Tauros. Depending on the level, I’ve seen them give at least 500 EXP.
Once you’ve obtained Cianwood’s secret potion, you can return here to battle Gym Leader Jasmine. She uses high-level Steel-type Pokémon that are resistant to most types of attacks.
The Gym Leader will ask you to travel west across the water to get medicine from Cianwood City. Agree to that, then use the elevator to reach the first floor of the lighthouse, where you can then head outside and begin your westward journey (grab the super potion before exiting the top floor!)
Olivine GYM. The gym is located at the north end of town. Unlike most other gyms in the game, upon entering this gym you won’t find hostile trainers wanting something from you.
Exit Olivine City through the west to get onto Route 40, a small vertical route with some land and lots of water.
9 Jasmine: 15 years old
Olivine City’s Gym Leader is Jasmine. She is special as she is the first Steel-type Gym Leader in the series.
Once you defeat them, you will receive the Mineral Badge. You can use it to train Pokémon up to level 70 that will still obey you. There is not much more to do here. You can check out the place where the S.S.
The port town of Olivine City has a few interesting attractions – the lighthouse and the port for the high-speed boat S.S. Aqua. There is an issue with the lighthouse that you must address before you can even attempt to fight the town gym leader.
Gold, Silver, and Crystal
When first encountered, she is in the Glitter Lighthouse with a sick Ampharos and will not return to the Gym until her Pokémon is healed. The secret potion is the only cure for Amphy’s disease. The secret potion is given to Jasmine, who will heal Amphy alone.
However, there are two trainers guarding the stairs leading up, so be ready for a fight. Although you only need to access the switch on the left to fight the Hall Manager, make sure you fight the two trainers on the right side of the room as well.
Pryce always leads with his signature Pokemon Mamoswine.
Go west of Ecruteak. Along the way you will fight some trainers and here is an apricot tree. You will pass Miltank Farm where a sick Miltank needs 7 Oran Berries to heal.