good endgames to know?

Opposition, triangulation, basic checkmates - K+2 rooks vs king, K+Q vs king, K+R vs king, Philidor position, Lucena position, are the ones on the top of my head.
By the way, I've written the article on how we, lower rated players, should approach the endgame - something on active play and some specific examples as well. If you are interested, here you go:
https://www.chess.com/blog/nklristic/how-to-approach-the-endgame-first-steps-to-chess-improvement

check out the section on the Endgame here...
Improving Your Chess - Resources for Beginners and Beyond...
https://www.chess.com/blog/RussBell/improving-your-chess-resources-for-beginners-and-beyond