Long post is long! There's a TL:DR at the bottom.
So I had part of this written up as a reply to another post, and with the current trend on the forums I could have put it in any number of threads. I figured it would be more beneficial here, however. My first "new thread that is actually just a reply to another". Yay! Everyone gets one, right? Right (I'm known to be wrong on occasion. Right? Right.)
Now, you might not want to hear this but... People are poor due to lack of effort, unwise spending, or both. There's no invisible force that's saying "thou shalt not maketh thy gil!" that is holding you down and preventing you from earning gil. Well, maybe it's invisible, but it's not in the game. And it certainly doesn't use ye olde timey speak (maybe it does?) So where is it? It's in you! Yes you, sitting there in a fancy business suit sipping your fine wine. And you, guy who is brushing cheeto crumbs out of your beard, down onto your sweat pants and time-worn beanbag chair. And everyone in between. Especially the ones in between.
If you put effort into making gil, you will make gil. Not "might" make gil. Not "maybe" make gil. Absolutely 100%, if you put forth an effort and actually try to make gil, you will make gil. That's not to say you will make hundreds of millions of gil, and if you do it won't be fast. But you won't be stuck with the 250k or less that you get from doing your story quests. You'll make more than enough to get by comfortably and purchase some luxury items you didn't have before. If you choose to hold on to it and not spend it as soon as you get it, you'll only see your gil grow. First a million, then two million, then three million, etc. It might not come fast, but it will come. If you keep at it, you can be one of those people with tens of millions of gil. But it will take effort for sure, and money won't just fall into your lap.
"But if everyone does this, then nobody will actually make any money."
Well yes, that's true. If everyone on the server is all trying to make gil, that gil just gets shuffled around and nobody actually makes anything. But that's the thing: Not everyone will do it. Why? People are inherently lazy, and as soon as they see the work required, they will quit and give up, going back to simply spending and not taking the time to make money. This is exactly what is going on now in fact, and what goes on in the vast majority of MMOs. It even applies to real life. Most people make just enough to get by, and they leave it at that. Not many actually try to make more.
"There's very little gil being generated into the economy!"
Correct! But there are a lot of people out there generating it, and it all adds up very fast. This is where the above comment about people not actively trying to make gil comes into play. Even with little gil generation, there are still people earning tens of millions or more, simply because they're taking the time to make money while the majority aren't. This is how you can end up with "that guy" who is sitting on a mountain of gil. He's rich because people make him rich. You essentially make him richer by not trying to be rich yourself. He's making all of the gil that you could be making yourself, if you were to try to make it.
"What do I do to actually make gil?"
Well, that one is up to you really, and that's where a large part of the effort comes into play. You need to actually find what's profitable or not. Despite what some may think, there is always something to profit on. The market is huge, and there's always a demand for something that somebody isn't supplying. That's up to you to fill in the blanks and give people what they want.
"I don't have a lot of time to play."
Time is money friend! Naturally someone who plays all day can make more money than someone who gets 30 minutes a day, but that doesn't mean you can't still make money. Luckily for you, having lower playtime generally means less expenses and need for gil in general, so you're still going to come out ahead.
"This is a game, not a job."
Entirely true. It's a game, and games are meant to be fun. But understand that your version of fun might not equate to ending up with a Scrooge McDuck style swimming pool filled to the brim with golden coins. Effort = reward, and you don't need to put in the effort. But you're also not going to get the reward. That's just how it goes.
TL:DR for those who want it: If you try to make gil, you will make gil. If you don't try to make gil, you probably won't. Simple as that!