What is the minimum amount of a gift card that would need to be reported? Received a $50 gift card from my bank.

Because this is a gift given to a customer from a bank unless you receive a form 1099 you will not have to claim it.  Please see Hal_Al posts below for more information.

[Edited; 2/21/2018]

I thought the minimum was lower for gifts given to clients or customers, like $600 then it generates a taxable event.

Poster is asking about a promotional item from a merchant to a customer.  It's not really a gift. Depending on why it was given, it may only be considered a rebate. Instead of toasters, today banks give gift cards, for opening an account,  and they frequently send a 1099-INT to the customer.

If you don't receive a tax form, e.g. 1099-int, 1099-misc etc; it's safe to assume it's not taxable.