Get your CC-ed units to at least Lv30 before moving on to other units. They level fast till then.
Next get a healer and heavy armor to CC30 as well. Then go back to get another healer to CC30.
Your goal should be to get a core team before the end of the event. So you can get beatrika as a replacement till you get spica off the trading post. I'll skip silver archers, because you'll need 3 to CC spica and even more to AW them.
If you still insist on CCing a silver archer, i'll go with the soma that already comes with 30 aff pts. But if you accidently used her as fodder, dont worry. She will be fodder later away unless you are a premium collector, but u need lotsa monies for that.