How can I know the best time to buy Betcoin?

You can’t know.

Well perhaps you could if you subscribe to the knowledge base of technical analysis > fundamental analysis.

In which case, invest when 9EMA > x while volume < 300 after x before I go out for breakfast but only if someone buy 2 BTC after selling 1 WETH.

That’s my algo to know when to buy BTC.

But srs, the best time is whenever you want. It’s a great store of value when compared orignal FIAT.