If you want cheap souls go to 4-2 and just kill the reaper over and over - its faster to commit suicide than to use spell to go back to nexus.
and you can get platinium in 3 playthrougs - you can purify dragon god soul and then utilize it to learn the spell in one playthrough.

As for BlazBlue CS - i envy you - it will take long time before its released here(If it will ever be released here..). Is delta-11 much different from Nu?