Could some one explain how to buy best cables?

Money and cable quality have nothing to do with each other.
200-300 should get you all you will ever need. There are many on here who do this for an ego stroke, let them piss good money after bad.

In a way I know the answer since in my main system, I had to go thru similar trial and error process about 7-8 years ago. The cables I ended up with and still happy with are NOT the most expensive I tried. Even from similar makes, I ended up with 'cheaper' ones, because they sounded perfect for my system. At the same time the mystique of the most expensive cables from say MIT or Purist audio or Kimber remained. I remember Mr Dunlavy believed in simplistic and inexpensive cable designs. Since I am proponent of Dunlavy Speakers, I tend to believe his theories.

But still, regardless of price, is silver or gold or copper is better owing to the improved conductivity? If say silver is better, than I understand the price since silver does not come cheap. So there has to be some rational...

Just try some Dakiom 203 series stabilizers with the cables you already have... http://www.dakiom.com

I would buy Kimber Kable Hero interconnects and Kimber Kable 8VS speaker cables and forget about it. They are inexpensive, sound good, and your done. That's what I did. Then, upgrades can be elsewhere...or enjoy the music.
John Dean

Everyone’s system is different so what works for one will not work for another. Even if the systems are similar the rooms most certainly are not. Throw in personal likes and dislikes and it can get quite confusing and costly. Everyone is well intentioned with their advice but if you follow someone else's advice about what will work in your system you'll probably spend way more than you intended too.

My advice is to establish a baseline for the way your system sounds with good set of well respected but inexpensive cables like what Whoaru99 suggested with Blue Jeans Cable. They'll get you a complete set up for probably less than $100. After you lived with that for awhile and have a chance to learn what you like or dislike about them, get in touch with The Cable Company at www.fatwyre.com or www.usedcable.com, they have a loaner program. Tell them what equipment you have and how much you have to spend and they'll send you several different brands to try out in your system for a small percentage of the actual cost. Keep the ones you like or send them back and try some others. They have a huge database of what other people with similar systems preferred so they take a lot of guesswork out of the whole process.

You may find the extra cost for the boutique cables is worth it or you may not. You will know for certain what works for you with little financial risk and you’ll get an education in the process.

Hope this helps.