Millioncorn and La Theine Cabbage are, notably, NPC buyable (Aragoneu and Zulkheim regional vendors respectively, number of other places for each as well), while Boyahda Moss is not. You shouldn't need to farm or garden them up, since the quest is like a 95% refund of the money spent buying from NPC.
Only reason to use moss is if you're reallllllly in a hurry, and would rather have more net gil loss (although if you can get it for under, uh, 7200 gil/stack, then I guess you could have gil *gain* here) than make a few more trips to Selbina.
The quest will, with sufficient repetition, max out your Bastok and San d'Oria (and by extension, Selbina and Rabao) fame, and get you high but not (on its own) maxed Jeuno fame. So that'll get you Titan, Shiva, and Garuda quests. Maxing out Windurst fame will finish up Jeuno fame, as well as max out Mhaura and Kazham fame (netting you Ramuh and Ifrit quests). Norg fame will also have to be done separately, and that'll net you the Leviathan quest.
Not sure what, if any, fame requirements there are for Fenrir and Diabolos, as I long since had maxed fame when they were added.
Vilurum - Quetzalcoatl
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