Minimum skin value for deposits is ~$0.6 . Because of price fluctuations and updates, you may be able to see some variation to this amount. For example, a skin could be valued at $0,5 BUX and still be available for deposit.

Minimum real money payment for deposits is ~$3 depending on payment method.
Minimum cryptocurrency deposit starts at ~$0.6, depending on the chosen coin.

You can see the minimum amounts by checking out the respective Deposit sub-pages.