This is what I would do: go one album forward and two albums backward at a time, and see where it ends.
Now, I haven't listened to the albums today to check my impressions of them, but I think you can do worse than following this proposal.
So first:
- "Oranges & Lemons" for much of the same, and it's arguably a demn fine album in its own right
- "Mummer" for a softer or mellower, maybe even slightly contemplative approach.
If both are to your liking, you can then safely invest in "The Big Express" and start listening to:
- "Nonsuch", which to me seems a bit like a more developed, less '60s Beat, continuation from "Oranges & Lemons"
- either "Black Sea" or "Drums and Wires". Can't tell right now.
What I can tell right now though is that D&W contains glorious and single-worthy, more poppy songs like "Making Plans for Nigel" and "Life Begins at the Hop" as well as the quite less poppy "Roads Girdle the Globe" and "Complicated Game".
Whilst I love "Black Sea", it seems a bit less pronounced to me, and it has fewer Coiin Moulding songs, which normally complement Andy Partridge's ones.
If you like "Nonsuch" muchly, then I think "Apple Venus" and "Wasp Star" are very safe, and I believe they are great.
The ones I'd be most wary about from your experience are "White Music" and Go 2", as they are the earliest and most new wave ones. Now I love them, but I gather not everybody does.
All IMHO of course, and from hazy memory.