There are three knots I use that have covered all my needs as a casual camper:

Taut-line hitch

Sliding knot for fastening loads or setting guy-lines https://www.netknots.com/rope_knots/tautline-hitch

Bowline

Essential general knot for tying a loop. https://www.netknots.com/rope_knots/bowline

Square Knot

Used for joining ropes or just an easy to unite knot. For joining ropes you could do a sheet bend which is stronger https://www.netknots.com/rope_knots/square-knot

https://www.netknots.com/rope_knots/sheet-bend

There are a billion options so I recommend just picking a few and practicing until you can tie them quickly without references. You'll start to understand hope knots in general work and be able to pick up other knots much easier.

PSA: the square knot is notoriously unsafe and should never be used in safety critical applications. Ditto for the sheet bend.

If you care about safety, look for knots used in climbing instead.