Which pack should I get next?

It really depends on your personal play style, but I think Laundry Day is a good pack no matter how you like to play. Vampires adds a lot of new features, but if you're not into gothic or occult gameplay, it's probably not for you. For Jungle Adventure, it depends on if you want to really explore Selvadorada or not. I think that the world is 90% of what makes the pack good, so if you don't want to adventure, that probably also isn't for you. As for MFPS...I honestly think there's no reason to get it (just my opinion), as it doesn't have much content at all and very little new gameplay.