100 Triple won't solve your elemental defence problems though, will it? For that you would need the -aga spells.
In theory you do not need any magic, but as Remnant is asking how to make it easier to proceed in the game I merely suggested a method. What I neglected to mention was that you should discard the level one magics (fire, blizzard, thunder) when you discover level two magics (fira, blizzara, thundara), and similarly with level three magics (firaga, blizzaga, thundaga). This will keep your inventory small and neat by removing all unecessay and redundant magics.