Flint Stone is a horrible one to me because it isn't enough plus other people may do it before you and you'll have to wait a while.
The lady looking for something to cook is great early on because Trent Bulbs are so easy to get.
In Midgard Fire Crystals sell for 2,600 gil. Easy money there. Other crystals though sell for 600 to 1,000 gil. Still good money.
Bernie is EASY money. But before you go if you have a BLM above 17 use him to Warp or ask a high lvl BLM with Warp II to join you or else it's going to be a looooooong boring run
I don't know of any more quick and easy ones though. If you want to know of any sort of easy repeatable quests then *ahem*
Bastok Mine you can look for someone named Goroaw(spelling?) who wants you to get him a Quadav Helm from any that you've killed. He'll give you 900 gil.
You could go get a Dangruf Stone at Dangruf Wadi by searching around(I forget where but you can ask around) and Horatius will give you 400 gil for each you bring.
Kill some Giant Sheep the go to a fire made by Gobs in South G. and Cook the meat making a sausage and go to the Meatlworks and give them to Hungry Wolf whole pay you 300 gil for them
That's all I know :\