I love knots and practice them all the time. Keeps my hands busy. So many useful ones but a few I think should be need to know for the outdoors.
Bowline - making a non adjustable loop
Clove hitch - all around useful
Trucker's hitch - tensioning a line
Tautline hitch - for slindin adjustability
Sheet bend - joining cordage together
I'd also think square lashing and tripod lashing are good to know on top of these knots.
Don't let life get in the way of living.