What you should understand it that most crypto exchange platforms are perfectly a good place to purchase your bitcoin depending what you will be using for the payment of the transaction. Using fiat for the purchase, you might require KYC process by majority of the exchange platforms listed on coinmarketcap.com . coinmarketcap.com will provide you with the exchange platforms which you can purchase the bitcoin in the order of which platform has the highest market cap and volume for 24 hours. Most of these platforms have strict requirement of passing KYC before having access to their platform for transaction. But personally, I will recommend that you use Binance, Bittrex, and Kucoin. Yobit is also a bit good to buy bitcoin..