There is no minimum amount of MXN or minimum use period rules. You can buy with it as long as you have enough balance in your wallet in MXN to cover the cost of the purchase.
However, you will need to have a Level 2 account in order to apply for the card.
Please keep in mind that to request your Bitso Card, you must have a Bitso account with a minimum balance of 800 MXN. To learn more about how to obtain your Bitso Card, click here.