Board Thread:Card Unit Builds/@comment-23.255.138.19-20150317033419

I am pretty new and am working on a starter debuff deck. I am trying to decide between a HSR exacalibur i got from last event and the SR mars i got from lottery. i also have a SR Hervor. which should i use to kill archwitchs and are any of them good enough to blow all my medals upgrading her Attack 