There is no doubt that gil plays a vital role in Final Fantasy XIV or A Realm Reborn, and you are all find the most beneficial method to upgrade your character more easily. Here, the most valuable ffxiv gil making guide is for you.
Anyway, what you should be aware of is that do anything yourself is the only way. Level a few classes that complement each other, and turn a huge profit off the items you can make. For example, right now one of the best combinations is an offensive Class with Weaver and Miner. As a level 50, you can farm banemintes. As a weaver who has the 25+ level, you can turn that webbing into Dew Yarn.
In the second place, you can take the Dew Yarn and turn it into Undyed Velveteen. Sell the Velveteen, and all the money returns to you will be completely profit, since you spent nothing on the materials. Eventually you will run out of Lightning Shards, and this is where Miner comes in. When tapped out, take the Miner out and farm some lightning shards around the Ul'dah area. This is viable at level 1, but once you hit 20, the shard yield will double, making it much more efficient.
A player can farm through the three classes, craft and mine a steady supply of items without ever having to purchase anything from the market. As your crafter levels up, the chance to headquarter will also increase, making you much more Gil per synthesis and as Miner increases, you will farm shards faster, resulting in less time spent having to collect them. This isn't the only combination of Classes that can pull this off either.