How important are mouse pads?

depends on the table.

if mouse works good on your table, you do not need a pad.

A mousepad is nonessential, but far more pleasant than using a mouse without one. As long as you don't have a horrible pad, of course. Look for something with cloth on top, not too thick, and with a decent grip underneath - most desks have a better surface than a plastic mousepad, and if your pad slides around when you move your mouse then you're better off without it. But even a halfway-decent pad is a huge step up from scraping your mouse around on a bare tabletop. Don't judge them by their price - you might even find a very good one for a fraction of a dollar. They do tend to last for a few years in my experience, so if one you happen to like costs more then go for it. I personally wouldn't spend $20 just on a mouse pad though.

Depends on what you want to play. For casual gaming you might be okay even without pad in case you have a good surface on your table, however if you like to play games like CS:GO or Dota, it might be preferable to get a quality pad, 10-15 bucks might suffice though. I personally bought one of the cloth Razers for 35 bucks in 2008 and it still serves, so maybe the price on the expensive ones is not completely unjustified. Up to you. ;)

Mouse pad, I choose very cheap fabric (surface 1030 optical mouse pad) or leather one, you don't want mouse to be scratched or scratching table, right?

They are so important that I don't even use one.

I've been using the same mouse pad since 2008 I think. It's like a sponge of bacteria and uhmmm... stains. Coffee related stains I swear.

Unless you have a mirrored table you want to use it on they aren't in any way necessary

You should find a discount code for artscow mousepads. They are 99 cents after discount (free shipping too I think) and you can make your own custom ones :P I've been using it for a few months with no complaints

I use a QCK mass, it's a great pad. I mostly just bought it to avoid wrist pain, and in the long term it is cheaper than replacing the teflon feet on my mouse every year. It also happened to improve my aim in FPS games

Mousepad is little softer than table so hand is more comfortable being supported by it.

I feel really dumb, but I honestly never realised there were so many people who didn't use mouse pads. Ever since I was 4 (am 22) I've used at least cheap Walmart mouse pads (bought my first "good" one a couple years ago), or I'd get free ones from promotional things. I've just always had at least 4 extras lying around that I didn't even pay for..they just kind of accumulated over time..and I've just never tried not using one. At the libraries, school, friends houses etc. everyone used them so I honestly never really questioned it just thought they were kind of necessary to play on the computer.

a cloth mousepad will be better than those plastic ones.
it's advised to use mousepad to reduce wear and tear to the mouse feet/teflon (strip of plastic at the bottom)

Not at all. They're a bygone of an age long past. The age of rotative ball mice. For today's modern optical mice they're actually quite hindering, as most of them are shiny and the optical mouse moves like crap onto them. You have to turn them on the other side, which isn't much better because it's foamy and hinders the physical slide slide. But why would you use them? Optical mice work very well on the bare table. Even supposing that the table surface is too shiny or that you want to protect the wood it's made of, you can just take a sheet of paper and put it under the mouse. It'll work ten times better than a shitty mouse pad. Even when I sit in bed with my laptop, I prefer using a book with hard covers rather than a mouse-pad. It really is completely worthless.