The best way is to create an account with a reputable spot exchange, e.g. Gemini or Coinbase Pro. This involves going through KYC/AML (submitting your ID, SSN, mugshots, etc) and the more diligently you supply these documents the better chance you have of getting approved without an extended wait. I would start immediately, then once the ball is rolling you can decide if you want to accept the invasion of privacy/make an investment.
The biggest risk is being left out.
The fastest way is probably to use PayPal, they let you buy Bitcoin from them and sell it back later or spend it. This is a great way to get instant exposure with not much effort.
There are also physical Bitcoin ATMs with high (like 11%) fees, which are a last resort but better than not owning Bitcoin.
I should mention there is a fund called Grayscale Bitcoin Trust (Btc) OTCMKTS: GBTC that is a reliable proxy for Bitcoin. You can buy it through more traditional brokerages and it is eligible to go in an IRA/retirement account.
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