If u have an overflow of units or can spend a decent amount then maybe..but imo units are best used for masteries,energy refills and saved for runs in events with high difficulty for Ur roster to buy revives and other than that saved for holiday offers..there were some pretty good offered for July 4th...I guess next offers will be on Christmas so I would suggest saving for that
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Save units and use it on mastery cores amd full energy refills.
Chatacter specific crystals have such a low drop rate for character advertised, not worth it.