The list below is a list of repeatable quests.They are a legit way of making some decent money.
Bastok
A flash in the pan - 100 gil
Gourmet- 100 to 350 gil
The cold light of day - 500 gil
Mine sweeper- 150 gil
San d'Oria
Resist the darkness- 200 gil
Start a flame- 100 gil
The merchant's bidding- 140 gil
Windurst
Mandragoras tracks- 120 to 250 gil
Auction house mails- 50 to 500 gil
Teaching materials wanted- 250 gil
Wanna be friends?- 200 gil
Another way to make good money is camping NM's. NM stands for Notorius Monsters. They will con "impossible to gauage" but really some of them go from level0-75
Monster Level Drop Worth Spawn Leaping lizzy: 10 Leaping Boots
!50k-250k (depends on server) South Gustaberg
Bubbly Bernie 10 Steam Clock
500gil(Quest) South Gustaberg
Stinging Sophie 10 Beestinger
7-10k North Gustaberg
Geyser lizard 30-32 Steam Scale Belt
15k(depends on server) Dangruf wadi
Steelfleece Baldrich 60-75 Viking shield
800k-1million(depends on server) konschtat Highlands (kill this at 75 and ull be rich)
Stray mary 19-20 Marys milk AND Marys horn
Milk-10k Horn-100k Konschtat Highlands (easy kill)
Now another way to make money is choose a job you havent tried yet and get signet on you and fight till level 10 you should end up with 20k+ Because of crystals.
FAQ'S
Q:What is the best way to make gil in this damn game!....its impossible
A:No nothing is impossible(well almost) try camping NM'S or get a signet on you and go fight. Their is exploits/cheats but i will not dicuss them. Try and play as legit as possible or if you like to exploit then make sure its not around people and gm's will be on your !@#$%^&*.
Q:What are some good websites to get quests, missions, and maps?
A: Try
http://ffxi.allakhazam.com http://www.speakeasy.org/~sticks/ffxi/named/title.html http://ffvault.ign.com http://www.gamefaqs.com/ Also search google you will find many websites by typing "Final fantasy xi Guides"
This is the end of my guide i really hope someone learned something....