I would do airs or fire runes to level 44 rc. After that, craft nature runes until you can craft death runes. If you can't craft death runes because of missing quest, craft natures until level 82 to craft double astrals. Craft deaths/astrals until level 91 to see decent profit from double nats.
Sidenote: when I botted RC I remember the paint having a bug where it didn't show the right profit per hour.