You have already gotten great answers, but I will add that if you want to use the GC for mobile orders or mobile check out in stores, save the GC # and the EAN in a note on your phone to copy and past into the app quickly.
I would also suggest having a physical GC for each adult (or person who will be making purchases), so everyone can pay that way.
My last tip is to tell the cast member that you are using a Disney Gift Card when you check out. It allows them to set things up on their end for easy payment. At least that has been my experience!