Just want to point out, the fees are significantly less if you use GDAX to purchase bitcoins. You can move bitcoins from gdax to coinbase wallet or to your own personal wallet.

In coinbase there is a flat fee, in GDAX you only pay fees if you put a bid in, and there is no existing sell order on the books that would fill you bid. The reverse is also in effect, if you put a sell order in, and no existing buy orders meet your order, there is no fee when the transaction takes place.

GDAX is an exchange. Make sure you are comfortable with using an exchange. I'd recommend you always use a limit order if you are just starting out.