Not sure how populated your server is.... but a QUICK way to make some gil is by going to a popular city and picking up items from the wards and selling them for a profit in the more less populated cities. Sometimes this is opposite so be careful. On my server this looks like... going to Gridania and getting Zinc ore for 300 gil a pop and then bringing it to Uldah and selling for 1.5k gil a pop :-) Doesn't take much gil to get started :-)

On my server it is also very popular for people to pay 50k+ for a teleport to other cities instead of using their own anima. Make a second character, have a friend teleport you to each city to get the crystals and then shout your services :-D

I feel like I'm whoring myself out here lol....

A more legit money maker... like previously said... do all your leves.. at rank 30 you will be getting about 20-30k a pop on most battlecraft leves and sometimes you get armor etc that can sell for an additional 20-50k.