In SP, for any victory type, Pottery usually is the best very first tech.
You can almost always pick one tech right after Pottery other than Writing (such as Mining OR AD) without delaying library construction at all.
It's almost always more important to get the tech(s) for your two or three nearby luxury types than NC, but Philosophy is indeed the top priority once you have done that.
NC is much more important than Stonehenge, frankly I wouldn't attempt to build Stonehenge at all until after NC is completed.
+++++Bronze Working should wait until after you have Philosophy. I would instead recommend getting Archery before then if you are either having barb issues or starting next to the Zulus.+++++
There is a backfill of several techs to be down at that point, I usually stop the backfill and go to an Education beeline via Civil Service after I have techs for Colosseum / Comp Bow + Circus + (with a coastal city) Lighthouse. (If you've NOT gone Tradition, you should add tech for Aqueducts after Civil Service. Tradition gets four of them for free even without the tech. )