It really depends on how you approach the sport. I can do knots pretty well, but I look at it like this: The more time you spend fooling with knots is less time the fly in on the water. I don't use tapered leaders, I use furled leaders. Furled leaders have a loop on each end that makes things a bit easier to change out.
I learned the Arbor Knot (to attach the backing to the reel), the Nail Knot (to attach the flyline to the backing and a piece of Amnesia to the flyline) and the Perfection Loop (in the Amnesia to connect the furled leader to in a loop-to-loop connection and in the tippet to connect to the furled leader in a loop-to-loop connection).
I don't do any salt fishing so I can't speak to any knots you might use there.
Knots are not hard to learn and they're critical to keeping fish on your line.
The better you understand them and can tie them, the quicker you'll be at it.
The best knots are ones that you're confident in tying, so the more that you're familiar with, the better off you'll be in choosing ones that work for you.
You don't need to memorize them all, knots like the arbor knot and nail knot you'll most likely only use at home where you can look them up.
To start, I suggest you learn a couple of knots used for tying different sized pieces of mono together. The double surgeon's knot and the blood knot. The blood knot is superior, but it takes a bit of dexterity so the surgeon's is a often a better choice in the field.
Then try a few loops to see what works for you. The non-slip mono loop, the surgeon's loop, and the perfection loop are all good for different applications.
And probably most important, try as many terminal knots as you can find to determine what works best for you to attach flies.
I use the basic clinch (with varying numbers or turns) and the non-slip loop. 90% of the time but everyone has their favorites
They have written instructions as well as video of how to tie almost every knot.
As for knots to learn, I only use Albrights, nail, unis, and seaguar knots. I am not a fan of blood knots for connecting leader to tippet as they are tedious, and pretty weak as well. Seaguar knots are a lot faster, easier, and much stronger.
Sorry, had to include that econ, got caught up in the battle between good vs evil.
Anyway, if you're looking to keep it as simple as possible, then you don't even need the seaguar knot. Uni to uni knots are still stronger than blood knots, and are at least easier to tie.
"Three-fourths of the Earth's surface is water, and one-fourth is land. It is quite clear that the good Lord intended us to spend triple the amount of time fishing as taking care of the lawn." ~Chuck Clark
I grew up fishing a "cast" of wet flies. That's the way my grandfather fished and that's how I learned. Nine foot cane rod, long leader, 'cast' of three traditional winged wets. A point, dropper and 'bob'
The dropper and "bob' flies were tied to the leader with a dropper loop.
Back then we'd fish a dark, medium, and light colored fly and rarely changed
The dark fly was a black gnat and that went on the point.
The dropper in the middle was a dark cahill, which is nearly identical to a hare's ear wet.
I don't remember what the light colored bob fly was. Maybe a light cahill.
I still fish that way occasionally in the right kind of water. It's deadly when done right.
The point fly anchors the "cast" in the current, while the dropper rises up like an emerger on the swing. The bob fly is meant to be dapped or danced on the surface, which can drive fish wild.
Three different flies in different parts of the water column gives the fish a choice.
In my home river, a peacock and partridge soft hackle is the practically the only fly you need as the fish key in on dominate hatch, the alderfly (zebra caddis).
Other than that, I still carry a few dark cahills and black gnats, but the wets that I use most often now are just generic fur bodied soft hackles