Thank you for your opinion, but I am asking because we are talking about an instant purchase which is the most easiest way to have bitcoins, the simple way to having bitcoins. Because I know there are plenty other way to buy it at below market price but I am talking about the best simple way to have it! Thanks for giving opinion
In that case, go with Coinbase.
Try not to use it with large amounts as their customer service is absolutely notorious, as I said.
If you are only looking to speculate for the short run, perhaps look at Paypal's virtual bitcoins as well. It is probably a lot more convenient compared to other crypto exchanges. Though, I would be very careful with holding these virtual BTCs in the long run as you don't hold your private keys (or any physical BTC through Paypal, for that matter). Your position is completely synthetic.