ok after speaking with some players in the game for the gocash gamer card is easy :
1º solution
go to www.ogpal.com
get account = go to categories =all category =search gocash = click gocah = after you have to choice 10$ 20$ 30$ or 50$ (but you can choice more like 3 X30$ or 2X50 $ect...) and dont forget to put with what type of money you will pay $ £ € ,after your choice just push buy button = and you wil pay with paysafecard or gyropay ,solo sewden/finland , cashU you have so many choice of payments , all payment have fee after that just wait and look the mail box , and go to the live support and get you pin code.
2ª solution
go to offgamers.com
get account = go to search/ find game = navy field (global) = gocash will appear and buy what you want 5$ 10$ 15$ 20$ or 100$ = buy code and payment method will be appear dont forget to put you money if is £ or € or $ again here you have so many choice of payment paysafe card or Ukash ect... is valid for brasil mexico argentine ... just look your country
i hope i have help some guys for take premium or ship prem :)
good luck guys XD