I want to start reading Superior Iron Man.
What is the ideal reading order for Superior Iron Man?
There are nine issues of Superior Iron Man and it doesn't have crossovers to other series. So just pick up #1 and read each issue in sequence.
You may have been confused by the "Marvel NOW!" (and "Avengers NOW!") labels. This isn't a crossover, but rather a company-wide branding effort indicating that new comics were being produced for the modern day, often with unusual premises that differed from traditional comics stories (like an evil Iron Man). Don't worry, it's not a crossover name or anything.
The main portions of Superior Iron Man's story is in:
Iron Man seems to be un-superior by the time of Bendis' run in the All-New All-Different Marvel Universe that came after Secret Wars.