As a Scout, sailor and member here I've always had an interest in knots, bends and hitches including trying to teach others, always in order of importance bowline, sheetbend and round turn and two half hitches these cover most of the important jobs. The hardest part of teaching someone to tie a knot is that unless they are switched on they cannot judge whether it is tied correctly, even if they have another example to compare it with. It's not impossible to learn from books, pictures but you'll have a bit more confidence the first time you rely on a knot if your previous attempts have been assessed.
Cheers