If you buy it for a low price, than you can sell it with a higher value and than you have a bigger chance to get some more money.
Can you please tell me which is best low to buy? or best high to sell? No one have answer of this as we cannot judge which is the best price to buy and which is the best price to sell.
That is because there is no magic answer. The best high to sell is relative to when you bought your low. If you want to make 40 dollars profit then the best time to sell is anytime it breaches above that from when you bought the low. This is for the traders. For everyone else pretty much now is the best time if you think BTC is worth more than it is currently going for.