http://www.ffxicalculator.com/
Has a good calculator. It is slightly out of date but if it doesn't have the spell you want, just find a similar spell with the same sc properties.
You might check my work on these examples but this is just one of each type I pulled that appeared to have some of the less crap WS's in it. Granted, you'll never get a 6 step with all good ones.
Darkness:
Red Lotus Blade > Circle Blade > Requiescat > Savage Blade > Chant du Cygne (E) > Gravitation spell
Red Lotus Blade > Requiescat > Red Lotus Blade > Circle Blade > Requiescat > Distortion Spell
Light:
Expiacion (M) > Burning Blade > Circle Blade > Requiescat > Savage Blade > Fusion Spell
Expiacion (M) > Red Lotus Blade > Expiacion (M) > Burning Blade > Circle Blade > Fragmentation Spell
Honestly, not finding any good source for a list of all spell properties. BG wiki has most spell's properties listed but not all of them and not in an easy order to decide on a SC with, especially the newest ones. I'll try to look some more later but it's getting late for me.
Edit, accidentally put Grav twice.
And Edit again... Put the wrong one for Frag. (maybe now they are right ^^;)