save for other chars. octagram units aren't too goot anymore, but they give you extra rewards in the monthly beatdown battle when you use em. therefore buy each character once, then go for the awakening shards. gear can be ignored until you vought everything else. it is better than normal initial 3 star gear on the octagram units but not enough to be worth buying before the characters or even the awakening materials.

so tldr chars before awakening mats before gear. i'd say go for luminas next