Card Packs are the best way to get powerful Cards in Romans and they can only be bought with Trajans, the premium currency of Romans. You can find out how to purchase Trajans here
Once you've got some Trajans to spend on card packs you'll want to:
- Click the Store button, just below your Seal/Rank in the top left of the screen
- Scroll to the Card Packs section of the Store
- Click on the card pack you'd like to purchase
- Input the amount of packs you'd like to buy (you can do this is +1, +10 or +100 jumps)
- Press buy when you've selected the amount you'd like (Buy option will only be available if you have enough Trajans to complete the transaction!)
Congratulations, you now have some card packs to bust open, back on the Card Packs section of the screen, head to 'Open Packs' to rip them open and see what powerful cards you've got.