You could partner with RaiseRight (gives a rebate back on physical or egift cards from certain vendors).

We need gift cards for gas, clothing items, toiletries, etc. This would be a great addition.

This is actually a very great idea. We personally use gift cards to offer meals, rides via Uber/Lyft, or to purchase self-care items from local stores. It also helps immediately display what the donation will be used for, since it's restricted to whatever the gift card goes towards.