If you have an account on a central exchange, you can buy Bitcoin at any price you want, at any time. If Bitcoin is not legal in your country, you can secretly purchase Bitcoin from any exchange, select a wallet of your choice, and hold it there. Remember that you should never keep your Bitcoin on a central exchange because the exchange can face any unforeseen situation at any time. You can select a wallet and save the wallet's security system in a safe place or write it down on paper. Remember that your wallet's security system cannot be shared with anyone.