First, remember to level up your soul cultivator level at camp. Soulforce tab, then Cultivation tab, then whatever.
Second, keep attending lectures until you can buy a manual for the daoist sub-path and a manual for the body cultivator sub-path.
Third, buy the daoist manual. (Nothing wrong with grabbing the body cultivator manual, too.)
Fourth, check, the soulforce/sub-paths tab to see what you need to buy.
Fifth, buy them in the cultivator village. This can get pricey.
Sixth, level up your daoist with the soulforce/sub-path tab.
Do you know how to become a grey sage? You might like it better than necromancer. Or might not. I'm a goody-four-shoes.