Sure.
I'd say all four are good starting points for different reasons, but the first three seem to work better generally then the latest album.
Frames is probably considered their best by the majority of fans, I would say that it is an 'album-album', in the way that all songs are really great, and you don't really want to skip one.
It displays most of the band's different styles and influences, and overall it is fairly progressive.
Everyone Into Position is comparable to albums like In Absentia and Images & Words in the way that it's more "easy" to get into, because some of the songs are more accessible, something the band has gotten both good and negative reviews about.
This album has a good mix of easier and more 'straightforward' songs, and some really long and epic, progressive-songs.
Effloresce is their debute album, and I would probably say that it's their most progressive studio-album, sound-wise.
It has a lot of really strong tracks, combined with a few instrumental shorties in between, and overall it has both shorter and catchier tunes, and longer & more progressive songs.
You really can't go wrong with any of these, so just go for what sounds the most appealing for now, and if that one doesn't click, you can always check out any of the others.