Some basic things you can do to acquire gold is gathering resources. Mining and lumberjacking can be extremely profitable. You could specialise in either the resources themselves or gathering the frost wood runic tools.
If you are after just bulk resources then Felucca is where you should try to gather them. For the Runic Tools Tramel is the best location to gather them.
Making several characters, preferably on a separate account, that does nothing more than gather the Bulk Order Deeds either to sell to other players or for you to complete can earn a steady income.
Certain dungeons you can run through very quickly can be surprisingly profitable in just plain gold, not to mention any augments that you find while going through them. For example, Bedlam in Malas I generally make approximately 30k-35k in just gold per run without killing the peerless boss. More is then made if you collected all of the gems and even more could be made if you were lucky with augment loot drops as well.
Some of the repeatable quests, have rewards that are popular with new and veteran players, such as the Orcish Forge and Ice Cross Power Bow. These are generally sold for 30k-50k.
Some of the long lasting quests such as the Vampire Hunter Quest for the Cleric Spellbook, which sells for roughly 6.5 mil, can be done over time