Questions on Materia

[Jeeqbit]

Although you can probably do all content without materia, it's a good thing to do because it's free damage and shows you are trying to contribute the best you can.

It's not worth worrying about until level 80 because you're going to keep changing gear every few levels, and most of the time you sync down to a lower level in dungeons, which makes materia useless.

[ItMe]

Please note though that when you level synch your gear doesn't apply any materia bonuses.
Depending on what content you're running and how fast you might be outlevelling the story it might be worthless to add materia onto your gear now.