At low lvls, worry not for materia, HQ gear can take you along pretty easy.

At high lvl is when things get interesting, and by interesting i mean hard.

People used to do CM runs to lvl up their bonded gear,the 1 star gives you the coveted rank 4 materia which also sells for oodles of gil, or the lvl 48 gear can also give you rank 3 which is not so bad and it can be gotten faster.

I do WP runs with lvl 48 gear, and i get a few materia every day if I keep making gear and spiritboding it.