You might need a lot of items to win the battle as it will constantly use Sporefall: also, to avoid this, spread your characters out as much as possible so some of them will avoid the status effects caused by it.
I’m not sure if you have access to Esuna yet, but if you do, buy it and use it regularly to counter Sporefall.
Elder’s main challenge is in the status ailments I find, so if you can conquer these, you should be OK.
Note: If you really can’t beat him, you can dodge around, and return at a later date. Head to the southern part of Golmore where Hellhounds and Coeurls appear, and flee past them until you reach the Feywood. Then, flee past the enemies in here and head east – you should reach the Paramina Rift eventually. (You might want to check a map, I’m not quite sure of my directions). However, I don’t recommend this – it involves fleeing past some seriously high level monsters, and chances are you’ll be killed on the way.
Closing.