Start with This Nation's Saving Grace I reckon, then basically any other 80s album. Hex Enduction Hour is probably their best and Perverted by Language is a big fav of mine. Their 80s stuff is generally untouchable for the most part (the 2 from 79 are also v good).
If you've enjoyed some of that stuff then there's been some good ones post-2000. Real New Fall LP and Your Future Our Clutter are my favourite later ones (the latter is the best the current lineup has done), or The Unutterable for some more electronic bits if you like.
The 90s stuff is decent but largely more expendable, best left to the end if you're still interested in exploring at that point.