I'm looking to post on Mondays and Fridays, and probably in the evening. I'd say if you update once a week maybe on weekends, but if it's more than that I'd spread out updates so you can hook readers more easily and consistently.
I remember there was a really good infographic on ideal posting days and times on certain social media, so that could be something to look into. But eh, there's people online all times of the day, so a consistent schedule seems best!
Anyways, here's my comic-baby, though official launch is still about a month off.