The higher your level, the quicker you will build up money. With that in mind, the sooner you reach level 80, the quicker you will reach optimal return of money/time spent.

I'd advise as Alethia that you do all the quests of your level ranges, that will give you the necessary coins for leveling (i.e. horse, largest bags, some cheap blue gears from trader to complete your gear already gained from questing).

At level 80, you will have more options to increase your treasury.
Ressource gathering of last tiers, recipe farming, and if you are premium questing in Khitai and shard farming. Crafting is an alternative too. It will basically depend on what your class is most efficient at, and where goes your preference.