There are hundreds of Bitcoin exchanges which anyone can sign up for and start buying Bitcoin quickly and effectively. Personally, I use Gemini or Kraken. Gemini has an excellent interface and low fees, while Kraken offers some of the best crypto assets and is one of the oldest exchanges in existence.
The real question is... What is your favorite Bitcoin exchange?
I haven't tried this Gemini exchange, but I am more on security and profit sharing, that is why Kucoin for me is the best exchange in the market, even if it is not highly ranked in the market, the security is awesome, profit sharing is great, it's everything you are looking for an exchange, the support I forgot to mention is top notch.