I don't know if Postcron is good enough. There seems to be some issues from the reviews given online. Buffy seems good, but I'm not sold on it.
Hi Allan here who has made tutorial presentations for social media automation applications. I would like to suggest Hootsuite and IFTTT. These are two easiest automation tool for social media. If you're using desktop, Gramblr is best for Instagram automation and scheduling. Thank you!