Yes, it is possible for your friend to buy books for you. You can also buy books yourself if your friend is willing to let you use his or her Amazon account.
You would have to register your Kindle to your friend's Amazon account. The account would need to have its "1-click" setting activated, and this would need to be associated with a credit card which presumably would have to be other than a Romanian card.
If your Kindle has wireless access, you can then buy the books yourself and have them sent straight to your Kindle, with the payment being charged to the above card. Or, you can buy the books and have them downloaded to your computer, and then transfer them via USB.
A third option would be for your friend to buy the books for you, and send them to you by email, adn then you transfer them via USB.
An alternative option would be to use Amazon gift vouchers to buy the books. But you would still need to have a credit card associated with your 1-click payment method, and if you can't use a Romanian card, you are no further forward.
One last point: You don't have to buy your books from Amazon. Although Amazon have the largest selection, there are other vendors, as well as a huge number of public domain books available for free download.
Hope this helps.