Bought pretty much all of them, I'd recommend them in the following order if you aren't buying them all:
The Future Past pack and the Scramble Pack are great for some more character interaction. Future Past requires a bit of strategy to pull off perfectly, while I was probably vastly over leveled for any of the Scramble maps to provide a challenge.
Lost Bloodlines and Smash Brethren give access to the Dread Fighter and Bride class respectively. Though I wasn't really a fan of old Hubba and his cards, even if he was determined to break the 4th wall.
I have the other packs too, but felt I could take or leave them. Maybe the Challenge Pack if you want a lot of gold to kit out a jerk street pass team. Some of the writing in the Challenge Pack also almost made me giggle.