The first thing that people need to realize about currency is that currency that's given to you by the game only matters to the extent that there's some thing to spend it on.
So, although the initial temptation is to say that gil is "easier" to make in FF14, because guild leves reward thousands of gil per completion, what you have to remember is that the raw quantity of gil is meaningless without some context. Having 20 million gil might seem like a lot unless every one else also has 20 million gil, then it's just average, and no better than if you and every one else had 1 million gil instead. After all, if every one has a lot of gil, then there will be a lot of gil "chasing" each player supplied item in the game, and prices will be very high.
In fact, the only reason that gil has any value at all is because it is taken out of the economy by NPCs. Since NPC prices will tend to be static and PC prices will tend to fluctuate with the supply of gil, it is the cost of NPC services that creates a value for gil in the first place.
So we need to wait and see what gil can actually be spent on before we can comment on the real ease of obtaining it. Imagine that a trip on an air ship costs 100,000 gil per trip, and leves continue to reward only a few thousand gil per completion. Suddenly, the cost of an air ship ride is sky high, the value of gil is incredibly low, and gil is "hard" to make (that is, it's hard to get enough gil to buy the things whose price does not fluctuate).
In terms of gaining a relative advantage in wealth (having 100 million when every one else has 20 million) there's not much of a secret to it. Figure out what other people want, so you know what they'll pay the most for. Provide those things for them. Spend your money on increasing your ability to provide the things that people want, rather than on trinkets that you don't really need. Basically, make as much money as possible while spending the least. What do people want? They'll want whatever makes them most effective, whether that be armor, weapons, food and drink, potions, ammunition, or any thing else.
Consumables have always been a good way to make money in any MMO, because the market will always exist, unlike the market for lasting goods which can become glutted over time. Consumables will rarely make you rich quick, because no one will use consumables that they don't think they can replace, which means they can't be too expensive. And yet, as long as they are being consumed, there will always be a demand. The market may have a glut or a shortage today, but as people move in and out of the market, it will equalize. Consumables make nice steady income over time.
Weapons, armor and other permanent equipment tend to be boom or bust. One of the quickest ways to get wealthy in any MMO is to find a good that is in high demand, quickly obtain the exclusive ability to provide that good while the market is hot and the cost of entry is high, and crank out as many of that good as you can sell for a high price. As soon as more than a handful of other people can provide the same enduring goods that you can, the market will generally yield to competition (unless every one can be convinced to join a cartel). From that point on, the profit for such items will tend to decrease relative to the cost of components. One can still make good money crafting a good, but the ability to do so will more often be tied to the ability to obtain ingredients at a better price than the competition.
Another way to make money is by providing raw materials to crafters. Being a gatherer has down sides, because you are ultimately tied to the demand of crafters. If no one wants what you have to provide, or they are able to effectively force a small price upon your good, you have little recourse but to accept their price or simply hold onto your goods. As such you are at the mercy of the whims or crafters and the market at large. On the plus side, by gathering, you risk very little except your time. You do not have to make any tricky decisions about how many raw materials to stockpile or when to purchase them for a good price. You simply head into the wild and gather the materials for others, and you make what the market will bear. Even if you make a disappointing amount for your efforts, you will never actually take a monetary loss. This makes gathering an even safer endeavor than crafting consumables, though often times less reliable.
There are of course many other methods to make money. You can simply kill enemies and sell what loot you find, often called "farming." You can play the market itself, producing nothing, but buying items that are being sold below their market value and re selling them at a more "fair" price (and pocketing the difference as your fee). This is probably the riskiest method in any game for making money, but it's also potentially the quickest way to get rich, if you're good at it. Being good requires a LOT of effort and a strong understanding of the marketplace, as well as a relatively stable economy.
The bottom line, no matter what strategy you pursue, is to know your goals, have a plan to achieve them, and keep your eyes on the prize. Very few people have ever gotten or stayed rich, in real life, or in an MMO, unless they made it a priority.
Edited, Aug 31st 2010 10:13pm by KarlHungis