Buying FFXIV Gil is a good means of driving forward the gameplay of your character in FFXI online, especially since this allows you to grow faster than any other player in the game. Some may consider it unethical, and some just plain nasty, but I say if you choose to spend money on something that is important to you why shouldn't you? In any case many people try to get better in the game; some do it by choosing to bribe friends to loose against them in order to gain EXP, others buy Gil from real businesses and some try to hack the game. If you really want to become better at this game, you have to do what you have got to do, and one good way (where you actually still have to play the game yourself) is buying FFXIV Gil.
Of course you'll still be playing the game, and everything like EXP and battle experience and quest achievement still remain your responsibility, but everybody knows how hard it can be to find enough Gil to buy something you really need if you have got everything else ready. It's just plain time-wasting if you ask me, and you shouldn't be forced to play around for hours without end just to get a large sum of money. Buying it is far easier.
Now of course Gil is artificial, even virtual money only existing in computers, and transactions in Gil are hard to control, especially since you do not necessarily stand a chance to get your money back once someone took you for a ride since essentially what you're doing is deemed illegal by the game creators. But there are a lot of legitimate businesses out there which are concerned with exactly this: accumulating Gil money from home and then selling it for real money, and since these people are mostly poor people from India or other Asian countries, I'd say give them that money for their work. It's actually quite well paid over there and I think it sure beats working your ass off in some copper mine.
If you want to test whether a service is actually legitimate and trustworthy or not, the easiest way to do so is to firstly write to the customer service and see how professional they seem and to secondly look for some reviews on the internet of people who already bought from them. If people already had luck using their service, chances are you'll be satisfied, too. In any way, buying FFXIV Gil is an easy way of advancing in the game.