Step 1 : become an omni crafter
Step 2 : get bored of gathering stuff
Step 3 : use the marketboard for everything
Step 4 : contemplate how the fck did you manage to be poor even though youre a crafter
Step 5 : get addicted to housing

At least thats how i manage to reach having 5k gil from time to time. Have you guys ever traveled from ishgard to goblet on foot?