cataclism: The thing is, these virtual cards expire quickly and mostly can only used for 1 time. It is possible to make a card that can be used multiple times for one store but even then the money associated to it is limited. I'm free to choose the maximum ammount but the thing is, I've been choosing smaller ammounts like €5 or €10.
I can recommend Entropay.
There are some bad user experiences about the service on the net, but personally I am a very satisfied user.
You can get a virtual Visa in few seconds, and the best thing is, you can have the same virtual card and same card number and just load money to it from time to time. Like PayPal balance.
It really helped me a lot when my credit card payments got denied when trying to use my card with British Kickstarter. The weird thing is, I was able to use my card with "normal" Kickstarter (Amazon payments), and I was also able to use that card to transfer money to Entropay virtual Visa. But all attempts on British based Kickstarter projects failed.
Virtual Visa helped me out, and even though I lost a few cents, it was still a good choice. A virtual credit card from a local bank would have had an opening fee of 10€, so it's not really even an option...
cataclism: I know GOG doesn't store card info but just in case, can this get me in trouble?
Don't see how it could cause any trouble.
If you can use your virtual card to pay, GOG is happy to get the money, and that's the end of it.
I haven't ever used virtual cards on GOG though, so can't speak from experience here. But as credit card information is not used to identify anything, there shouldn't be any issues even in theory, other than your credit card, virtual or real, not being accepted for some reason.