Because these are some of the most commonly asked questions we get, here's something to serve as a starting point, perhaps:
My personal preferred go-to setting book for actual play is the Blackmoor d20 hardcover by Zeitgeist Games, from 2003/2004.
My personal choice for one of the best "unlabeled" adventures for Blackmoor would be "The Doom of Listonshire" by Ari Marmell - sold by Kentzer & Co, if I recall correctly.
My personal system of choice for Blackmoor-related one-shots is usually Solomoriah's Basic Fantasy RPG, as available via this website:
https://www.basicfantasy.org/(I'm mostly playing the DCC RPG, these days, but that's a relatively recent change.)
--- Mind you that all those are *my* choices, not necessarily *the best* choices one might be able to make, and that they are based on my interpretation of the setting which might positively not match your own. :)