Create an account on a trading site. I’ve generally had good experience with gemini.com. You’ll have to do the whole legal process of confirming your identity with a government ID because they report your profits/losses to the IRS for capital gains taxes. From there, you can use a credit card or bank transfer to buy. Once you have some, you can try to transfer it to another wallet or another exchange to “anonymize” it, but keep in mind that it’s all traceable given sufficient effort by someone trying to track it down. Some currencies are better at hiding that stuff (Monero, maybe?).

If you really want something close to anonymity and quick and easy, your best bet is to find someone you know in real life and give them cash to transfer to your offline wallet.