Bitcoin (BTC) price abruptly dropped 4.9% from $9,800 to $9,324 after rejecting at a key resistance level again, is it a buy the dip opportunity? 
Are you sure that currently price is already cheap? It will be better you make your own analyst first before you buy it. You can use trend line strategy to make sure that the price is already lower or not.
The basic strategy to get profit is, buying cheap and sell high. But it is not easy to make sure that the price is low or its pricr will goes to lower than that. But if I predicted, its price will goes lower than that, given its price was stable at $9600-$9900 in a few weeks.