We used Disney Reward points for anything that wasn't on the dining plan, like beer and wine, and souvenirs. You can also apply it to your MYW package, and then pay the balance using another method. Before you get a card, call and see when it will expire (you don't want it to expire before your trip!). And then put the minimum on it (20 points). Right before you go, put as much as you want on the same card, and you will be set. Since you can only transfer 20 points at a time, it helps to wait until right before you go.
We used our dining plan when we could. I didn't want to leave with a cs meal or any snacks left. If you can use it for snacks at Beaches and Cream, I would. Don't forget that you can use snack credits at the resort stores. I did this to buy a larger milk than I could get in the cs restaurant (at WL). It was more economical, and I could keep the milk in the room in the fridge (for cereal for DD6 and to drink for DD2).
DD6 had Disney Dollars to spend, given to her by her aunts, and it was a great way to limit spending. I set expectations with what I would buy and that she could buy anything beyond that (until she ran out of Disney Dollars). So she used it at the shops.
I don't know about the gift card.
Enjoy!