Best way to make gil is to have a 75 job.
I made 200k in 45 min total(including the walk) getting 2 coffer keys in eldemine
They didn't even have to fight, I just made them hit the switch for me than go hide somewhere safe. 75mnk/nin powah.
The good money I make is in den of rancor. Let me say that FEW people can do what I do cause of my job and play style. Even if you also had a 75mnk/nin you might lack the merit points/equipment/skill to pull this off. I basically run around there and kill everything. I get lots of KS (seems like you get more in beastmen controlled areas). I get lots of conquest points. I get coffer keys which can be traded for astral rings. I have like 65 clothcraft, I could probably do something with the 500000000 tonberry coats I toss
I don't know why I'm so good for it. I've had beastmaster, ninja, and summoner friends go down there just to die
The astral rings are not good by themselves(in fact, if that was all I got, it wouldn't be worth the trouble).. whats great is I can trade 99 kindred seals in for potentialy 15 million gil. Last KS99 run I did I made 4mil. I never get lucky and get kreisgsbell on my orb :/
Not to mention that.. being in a HNMLS I can have my linkshell kill anything that drops anything I want so I don't even really need gil.
In the grand scheme of things.. most items you will want end game are rare|ex so..
The downside is.. being 75 is expensive. Your LS will expect you to sneak/invis yourself. My oil/powder budget can litertly be over 100k/day sometimes. Food is expensive. You have to pay 3k+ for choco cause no one is going to wait for you to walk. Regional Teleport Fees, Echo drops, Hi potions, Antidotes, Holy Water, Icarus Wings, Shihei.
When it comes to making gil.
1) Don't count gil/hour ever.
2) Count fun/hour.
3) Look for something that only you can do best.
4) Multitask.
5) Crafting is not good money.
When it comes to point 5, thats not entirely true. Crafting is a GOLD MINE (to farmers). Go to allakhazam and download a few guides for crafts. Let me describe the process.
1) Newbie reads about how great crafting is on allakhazam.
2) Newbie goes to a RMT site and buys 10 million gil.
3) Newbie pays waaaaaaaaaaaay too much for raw materials.
4) Newbie ends up with a moderly high craft and complains that he can't make gil.
Here is where I step in.
1) Pro reads about how great crating is on allakham.
2) Pro researches items someone would need that wanted to powerlevel various crafts.
3) Pro puts items up for sale at ridicious prices on AH. They sell for some odd reason.
4) Pro ends up with a lot of money and posts about how great crafting is on allakhzam.
This is how I made all my money prior to 75....