If you want to add money you can always buy a steam wallet top up global code or a steam wallet top up Argentina code, I think you can top up your steam wallet before you change the store country to Argentina but I don't know if that works I have never tried it and if it works remember that steam will take a fee but I don't know how much. If you want to buy the games for your self and don't know how to do it or can't with the Argentina method you can buy the games from sellers in the forum. They will gift you the game. If you want to buy I recommend you to buy from clarkkent5 he sells steam games for a cheap price using the Argentina method. I have bought from him in total about 5 or 6 times. He will help you with everything.