spica is one of the best units u can get from trading post. I say get it. You will have a couple months of time to get dcs for chydis. She has very high base stats , and a good skill that can be maxed easily by the silver elf archer guy. Also she attacks around 5% faster then all other archers. ATm she's probably the second best archer in the game after nanaly. Also Archers are quite high priority , so unless u have better stuff , i'd get her asap. (PS , she also starts at cost reduction 1 i believe , compared to other plat achers)