Hey There im a new player, I started when the event of Lolonee was ending so im not that strong and I would like to ask for advice on how to lvl/CC my units (with my current team I keep loosing the 4th battle of the ongoing event "Ruined City") Im lvl66 dont have the matts for CC yet so my best fighters are

Archers
Bashira lvl50
Soma lvl42
Daniela lvl10

Soldier
Katie lvl50
Phyllis lvl49
Crave lvl22

Heavy Infantry
Leeane lvl37

Healer
Iris lvl38
Alissa lvl15

Witch and Mage
Belinda lvl30
Valerie lvl15

Bandit
Lolone lvl43

Lancer
Elaine lvl20


And i just spend all my SCs (freeplayer so only 50) and got box expantion (needed the room)
and this units

Feng Shui Master Mia currently at lvl 15
Hunter Stray lvl 20
Half-Elf Yuyu lvl 20
Priest Chrostopher lvl 30
Rogue Harissa lvl 30

Im thinking on adding all of them or at least Mia, Stray, Harissa and yuyu to my main team, and i guess i should try to lvl up Mia, yuyu and Stray since they are plat and gold units so my question is,
Should I buy a spirit of gold with the demon cristals? (only got like 20 or so) so I can CC Katie (and soon Iris) or
should I keep lvling my current team?, or start lvling Mia and Stray instead?

BTW current Team is

Katie
Phyllis
Crave
Iris
Alissa
Dorca (lvl9)
Bashira
Soma
Daniela
Elaine
Leeane
Belinda
Valerie
Lolone
Cypria (lvl20)