When it comes to buying then it would depend on what are your motives because we do have two different things in mind.

If you do talk about going for long term then theres no specific time for you to buy yet you can buy directly without minding on whats the current price that you have entered, since you do
go for long term or for years then it wouldnt be an issue and we would just sell out when we do already in profits.

If you do talk about for short term aspect then this would be a little harder yet there would be considerations before making any steps because
price volatility and being unpredictable would be your main enemy on here thats why you do need analysis neither technical or fundamentals
and this is where traders do differ basing of into their experiences,knowledge and skills.