Gift cards are one method of paying for items from iTunes - they are not available in all countries (and cards are country-specific, so you can only use cards that are issued in your own country), but where they are available then you might be able to get them from Apple, online retailers, supermarkets etc. You can continue setting up an account without a gift card code e.g. you can enter a credit card number as your payment method instead.
If you don't have a gift card nor a credit card then there are instructions on this page for creating a new account (it won't work with existing accounts) without giving a payment method : http://support.apple.com/kb/HT2534 e.g. select a free app in the store and click on the 'create Apple id' when 'buying' it.