Barby007,
Things you can buy now:
Rook City (Provides 2 heroes [Expatriette and Mr Fixer], two environments [Pike Industrial Complex and Rook City] and 4 villains [Plague Rat, Spite, The Matriarch and the Chairman]). The theme is basically street level effects in Gotham, I mean Rook City.
Infernal Relics (Provides 2 heroes [The Argent Adept and NightMist], two environments [Realms of Discord and Tomb of Anubis] and 4 villains [Akash'bhuta, Apostate, The Ennead and GloomWeaver]). The theme is magic.
Unity mini expansion (Provides 1 hero, Unity)
Ambuscade mini expansion (Provides 1 villain, Ambuscade)
Things you can buy when Shattered Timelines is available in May:
Shattered Timelines (Provides 2 heroes [Chrono-Ranger and Omnitron-X], two environments [Time Cataclysm and The Block] and 4 villains [Iron Legacy, Kismet, The Dreamer and La Capitan])
The Scholar mini expansion (Provides 1 hero, The Scholar)
The Assistant min expansion (Provides 1 villain, the Assistant)
Silver Gulch, 1883 min expansion (Provides one environment, Silver Gulch, 1883)
The Final Wasteland mini expansion (Provides one environment, The Final Wasteland)
Things you can buy in October when Vengeance is available:
Vengeance (Provides 5 heroes [Unnamed at present], 2 environments [unnamed at present] and 5 villains [Probably Ermine, FrightTrain, Proletariot, Friction and one unnamed {and which I personally think is the Vengeful 5}])
I think Infernal Relics is a better buy than Rook City, although both are good, but the IR heroes are definitely more complex than most. The villains are, however, slightly easier being mostly on a par with Citizen Dawn and Voss whereas Rook City contains the only two level 4 villains released so far (The Matriarch and the Chairman), so it depends on what theme you're looking for as much as anything. The Unity mini-expansion is probably more useful than Ambuscade and she is definitely a fan favourite character. But buy it all. You now you want to.
Can't talk in detail about Shattered Timelines but it will be very much worth it when it comes out in May.