What is the best and worst media discs to buy for Clone CD purposes?
Depends on your writer and not on CloneCD. High quality media is always recommended of course. On the website of your drive manufacturer you might be able to find a list of recommended media. I would go with that.
From what I heard, Memorex CD-Rs tend to give the best results for backing up games with Clone CD. I’m sure there are other high quality CDs out there.
I was told not to use non-name brands or those that come on spindles as these tend to be lower quality. When a mate tried using a generic CD-R with one game, the game would install but kept asking for the original CD, but when he tried a Memorex later, the game never gave any trouble.