it's only like 2% chance for silvers from 2k summoning, so getting a particular silver class out of it is rather tough.
I reckon you should now save up your stamina for thursday daily (in 3.5h) and farm DCs to get spica (no need to use SC)
after which just carry on leveling units as before. and maxing affection via phalanx 2 runs when it's not monday/thursday daily. you're done with this event. it's time to build your team for the next.
also, you can farm 3rd map (the pirates) for about 2 silver pirates, and 4th map if you need silver rogue/archer, and 1st map if you need silver valk