i do buy Bitcoins for resale again basically for my trading activity and buy when prices down and sell when prices rise up
You have to be a genius to figure out when prices are up and when prices are down.
$300 seemed to be a peak a few months back.
People will be dieing to buy at those prices right now.
Very rightly said, very difficult to predict the best price to buy, as we don't know what bitcoin holds for us very next day, so it totally depends on luck to buy and sell your coins.
We all buy Bitcoins because we think it has now a low value to buy it. If you can but it with a low value than the chance is higher that you can make some more money later.
But to predict a currency it is very difficult. You never know what can happen later in the future.