Normally you should not have a lot of money in your backpack.The easiest way to get money in Europe is undoubtedly with "ATM machines". It is recommended that one takes more than one method to retrieve money: debit card, credit card (Visa type) despite being more insecure if lost, and finally, some but not much money scattered among backpack, wallet, purses, etc.. It should be noted that the ATM withdrawals abroad usually require payment of a fee, sometimes around € 2.50. Therefore, upon arrival in each country should make an estimate of expenditures by the number of days of stay and just do a survey.
Budget
An inter-rail can be made with about € 1,000 (some do and others with 750€ 1500€) but it always depends on person to person. Some costs: