I only just found this but, in case you're still testing things, here's a couple of hints:
it is possible to navigate in the dark;
it is possible to climb even without stairs, so you can usually get out of subterranean pits even tool-less; it's extremely rare to get into an actual “save-ender” situation
as your tech level progresses, you'll discover ways to automate most things;
do focus on getting ore; there are hints in the rock to where it may be.
@HipsterTenZero @chloyster
I only just found this but, in case you're still testing things, here's a couple of hints: