don't waste silver archers to cost reduce other silvers. Archers are one of the most used fodder in cc. That being said , a lot of really good archers can be obtained even for free (duh , bashira is a free giveaway - unless you got kerry > whichi kinda doubt since you seem newer at this game - and spica is a 200 DC unit from trading post. Both are really good , but to cc a platinum archer u need 3 silver archers , so they are quite expensive)
PS: you can even get gold units from 2k summon (but very rarely). For example , i got a cyrus and a conrad from it. I think there was a guy posting in the 100 2k summons thread that he even got a platinum. Yes , on average , if you're lucky and got extra gold , doing gold summons can't hurt. That being said , i'd try to raise my gold piles now in preparation for awakening , since that is a very costly process.