You can buy it on exchanges like RoboSats.com or bisq.com

These are recommended because they don't ask for your OD. I made a long-form post here on how to use RoboSats to buy Bitcoin with Amazon gift cards for people new to the process.

You'll want to store your Bitcoin in a "non-custodial" wallet, meaning that you have the keys to the wallet. The "why" is because of you don't have your own keys, the entity that does can close, or empty, your wallet at any time. Ultimately, you'll want a cold storage (hardware) wallet for long-term storage.