Dont know if anyone else notice this or not, but when I was doing my flame trial/geodes I noticed that the lower tier mobs trend to drop geodes more often than ifritites. For example, I was able to get about 2-4 geodes killing Lesser Colibris out by the Waypoint outside of WG. But if I were to try to kill faster and kill inside Abyssea I trend to get ifritites instead. [Abyssea is faster due to repop timer].

So at the end, I ended up killing slower but didn't have to buy as many. Not sure if it's just me and 'luck' though.