What am I going to do with these dups? Does Gamestop offer you a penny for each and then sell them for $2?
The only solution I see currently would be ebay or craigslist/kijiji/equivalent in your area.
What I did with the first series (and intend to do with the next) is that I made myself a list of the cards I wanted, then I bought enough packs to have a little more cards than the quantity I wanted (to make trades easier since I had more variety to choose from). Then I put up for trade everything I didn't want, and once I had all the cards I wanted, I sold the rest as a bundle for a little less than $1 a card. That worked really well for me!
By the way, there's an Isabelle card in each of the 3 series, so brace yourself
The 3rd one is wearing a kimono and is super adorable