Don't get cought unprepared when you travel overseas; a credit card can be handy but it's a sweeter deal when you have one with all the perks. If it's your regular card you use better make sure of these few things:
you don't have to pay international fees transaction
you have an active PIN on each card you want to use - beware of the ATM fees, each bank would set up their own fee level
you have enough on your card balance or credit line in case your car rental takes a large amount as a security deposit - lately that can be even $800 - $900 if not more. Also rental company prefer you use the same card you used initially.
If you buy a cash gift card still make sure of your balance on it is satisfactory for large security deposits some places might ask.
There is always a great idea to have the phone numbers of you cards with you and know how to dial from the other side of the pond!