The short answer is up to two (2) hours the first time and then in less than thirty (30) minutes each time.
As soon as the VISA & MasterCard fiat transaction payment is completed with your credit or debit card, then an email is sent to the GokuMarket registered email address, which will have all the details regarding the transaction.
The purchased digital asset will be deposited into your GokuMarket wallet and as usual, it will need some blockchain confirmations before the funds are available for use. Please view the cryptocurrency deposit status in your wallet.
As per MoonPay the first transaction may take up to 2 hours and generally, thereafter it should take around 15-30 minutes. Please visit the below link for more details:
[Latest update 2020-06-20]