First of all, you must gain Ungaga as an ally. After you have him, you gotta get or build up to a Terra Sword. It seems that the Terra Sword has a bit of lucky magic in it. After that, go to the Divine Beast Cave and call forth on Ungaga while equipped with the Terra Sword on the either the first, second or third floor. Soon you'll be able to collect a lot of Tram Oils with just a few entries inside the cave. After you got all the tram oil you need, go to the back floors and keep collecting goods! ( I got seven tram oils with just two entries inside the cave! )