To buff yourself you can take even devotion, dunno why everyone wrote about DC robe set (I know, out of oly stadium you can't use devotion ofc :P And i know, that DC robe set gives best C.Spd boost). Hvy set and duals will be best choice for you, also summoning scrolls are good.
Yes... you fight on Sagittarius stats and when there's last day of month you make switch to PP... Then you go on PP stats to monument and "I Want to be a hero" :)