If you buy some bitcoin try to gain knowledge about bitcoin and crypto currency to get you familiar with how things work in this forum. If you want to buy the best time is when the price is low and hold for in the short or long term to be able to get big profits. 
if people say buy or sell do not believe right away, think again what is true and not true, whether you have to buy or sell bitcoin, not everything that people say in this forum is true, maybe some again just nonsense, if it comes with a logical reason you can trust it