I use Gemini.com. It's easy in that it doesn't add any additional KYC hurdles that any legitimate bank or exchange  uses.

It will take a few days to set up your account; like with other institutions it will validate your bank to make the transfers and then, once things are operational it's seemless.

You can send up fiat from your bank and trade for BTC almost immediately. The only restriction is that they will not allow you to transfer your BTC to another wallet for 4 days. The four day wait is common for all institutions (whether crypto or stocks). The advantage is that you can immediately purchase BTC at the current price.

Coinbase is easy but it's expensive.

You can go to bitcoin ATM and get it instantly. All you need is a driver's license and a credit card - but it's very, very expensive (not worth it my book).