refer to the above link by buttlover and check EthEternal's videos, he has a guide you can follow to clear story mode missions.
just take note that it would be best if you can get 2 50cc30 archers (bashira + soma/daniela), 2 50cc'd healers (iris and alissa) and 50cc'd katie. that should get you to clear the 3rd map (green dragon) which you can farm next week for fangs and hopefully silver soldier/archer, both of which are silver cc fodder units which are quite good to have more of.
would be best if you can make it to CR2 for claudia with some SC use, but if you can't make it, don't fret it. claudia will still be good to have even w/o CR/SU.