Question Time again. Just got a Plat tin can today thankfully and need some advice.

This is my Base CC'd team + Christopher who should be CC'd tomorrow (Not wasting a Tin Can on a level 48)

The question is what should I save my plat armor for?

Level 41(Skill 3) Claudia (Yes I know she doesn't CC)
Spica who I should have either this Thursday or next Thursday at the latest. (My current plan)
VH Khuri lvl 41 (I think I am good on ranged)
Dancer Marnie (only level 7 but can level pretty quick I am sure.)

Also if the answer is Spica (Which if I have been following along correctly on the forums I think is the answer.) Is Desert Battle better than Oasis since I will be getting Archers to level her?