Writing, if you plan on tackling that as a supermax, should be done when you have either a Moodlet Manager or the Motive Mobile. This way, you can remove the pesky hungry/sleepy/stressed/lonely moodlets. Make sure you abuse use it liberally. For mine, I also had Hates the Outdoors trait to avoid Stir-Crazy, and the Neurotic trait so that Justice could freak out, and then not get stressed for 8 hours.
As for the skill challenges, I just started to write 4 of each genre as it became available, and easily got the 20 novels challenge; I chose to Master Masterpieces, and writing about 10 was more than sufficient to kick up the $30k made from writing challenge.