Can't make purchase with gift card while family sharing

Someone please help out. So I'm part of family sharing, but as an adult with my own money I want to purchase my own things instead of having to ask the family organizer for their card information. After some searching I found that the only way to get around this is by buying a gift card and redeeming it to your account and making purchases that way. However I'm still having trouble. Whenever I go to make my purchase it tells me I need to verify one payment option. It shows my balance from my gift card and the family organizers card, but it won't let me tap to actually use the gift card. The only buttons it lets me tap is cancel or to enter the card info of the family organizer. I would appreciate any help in solving this. Thanks.