The minimum deposit depends on the payment system and on the account type you have chosen.
If you go to the deposit page and type "1" in the window for the amount of the deposit, and you will see a message that clarifies the minimum amount for the method.
For the Premium account, the minimum deposit is set to be 100$, for the ECN account, the amount is $500, for Cent account - $10.
For more information about the account, differences visit this page