It's difficult to say where I make my gil since I don't want to lose my market, but I guess my little bit of advice I would add is this:

Perhaps it's better to farm mats that can only be found in areas of the world that players tend to go less. For example, everyone loves uldah. Goods that are farmed in La'nasca or w.e might be a bit more rare, and sell better

Thats my advice, and honestly i don't know if it's true, but it works for me!

Shy Freedance