I’ve tried this when attempting to subscribe to MySudo via Google Play. I made a post about this a while ago. Google may block your attempt to redeem your code and ask you to submit proof of your purchase. Despite this, Google says the information is not “consistent” with my account, whatever that means. Eventually, I just used one of my Revolut cards. If OP intends to use Google gift cards, they should not put more than necessary for their subscription.