Do NOT do champion chains. Not only are they beyond boring, mind numbing, slightly nerfed (recently), repetitive, fun-sucking, highly profitable still, but they will make sure you become “greedy” and every content you do from then on will be compared to “time vs gold” ratio and how you could have been on that champion chain making 3 times the amount of money you are making by helping friends or doing other non-gold-profit stuff.
Dungeons is by far the best answer. Get a group of friends ( I made around 3-4 Dungeon friends who do dungeons on regular basis and we call eachother out before doing dungeons as our to-go guys, resorting to pug for the rest of the group.) It will increase exponetially the fun, but give you friends, ensure the group is “geared” and knows its stuff, knows your style, you know their style, might even team on some voice-chat.
Personally, I like the world boss train. In 2 hours you can make approx 15g. On my server, LOTS of people do this, and I always group up with friends or guild mates. If you enjoy dungeons, do that. If you enjoy “stock market ticker” play the trading post. Personally, I’m an accountant and the thought of more THOUGHT in my PLAY time is not fun… at all. Keep in mind that you will need most waypoints for world boss train. There’s nothing worse than being left behind because you haven’t been to a certain map/WP. Regular champ farming has died right off on my server in the high level area, so that’s not really an option anymore.