>>1366622>Must- know knots, all you need for sport climbing and top-roping:Rethreaded figure 8 (tie-in)
Barrel knot/double fisherman's (stopper knot)
Girth hitch (attaching sling or PAS to harness for cleaning a route)
>For trad, multipitch, and rappelling:Clove hitch (clipping in to anchor, best to learn how to do it one-handed)
EDK / Flat overhand (joining 2 ropes for rappel)
Catastrophe knot / overhand-on-a-bight
Prusik, Autoblock, Klemheist (know their differences, for example the klemheist can be made with webbing)
Bunny ears / Double fig-8 loop (quick n easy 2 or 3 point anchor attachment)
Various anchor configurations, pretty much all of which just involve overhands or fig-8s. Again seek qualified instruction
Knowing these will get you off to a good start. Stuff not covered by these knots is typically for rescue, hauling, or other climbing styles. Many of the knots are also essentially the same, just used for different purposes and thus have different names.