If you're going for one mostly-perfect bend or knot, make it the Zeppelin Bend[1] and the Zeppelin Loop[2]. Secure, fixed, easy, jam-resistant. It's not well known, so don't use it when other people need to understand your knots, but it's hard to beat for overall utility. If you need other people to understand it, use the Alpine Butterfly Bend[3]/Loop[4].

[1] https://en.wikipedia.org/wiki/Zeppelin_bend [2] https://en.wikipedia.org/wiki/Zeppelin_loop [3] https://www.animatedknots.com/alpine-butterfly-bend-knot [4] https://www.animatedknots.com/alpine-butterfly-loop-knot