You use fly
you go to olivine city
yes
You head through Ecruteak city and surf over to Mahogany town.
Cianwood City is across the sea from Olivine City (the one with the lighthouse). If you do not have surf, you get it at the dancing place in Ecruteak City. You have to surf from a beach to the left of Olivine.
The MooMoo Farm is North of Olivine city, And West of Ecruteak city.
Exit west from Ecruteak City. You will reach Route 38. Follow along until you reach Route 39. On this route, head south to rach Olivine City.
You surf [Of which you can do after beating morty from ecruteak] from olivine.
Follow the route west of ecruteak. At MOOMOO farm go south.
you have to bet team rocket at mahogany shop then you have done it dadarr or it will be in Olivine town and Cianwood City, which is on the other side of Ecruteak city. I think that these two gyms would be best though if they were the 5th and 6th gym battles. After you beat Chuck in Cianwood City his wife will give you fly, and you will be able to fly to Olivine Town or Ecruteak City
The Light House is located in Olivine City. You travel west of Ecruteak, and when you can't travel farther west, you travel South. It is located at the very southeast edge of Olivine.
technically its olivine city gym but jasmine wont be there until her ampharos at the lighthouse is better so you have to surf your way to cianwood city which is your next gym battle
Falkner - Violet City Bugsy - Azelea Town Whitney - Goldenrod City Morty - Ecruteak City Chuck - Cianwood City Jasmine - Olivine City Pryce - Mahogany Town Clair - Blackthorn City