You won't  need to worry about the singer, Paul.  Vocals are the exception rather than the rule where T.D are concerned.  That's one of the things that made the album I chose stand out from the pack, so to speak.  "Essential" is probably as good a place to begin as anywhere.  I'm not sure how you feel about "best of" albums, but it'll give you a decent idea of what to expect.  T.D. did change quite a bit over the years, but Spotify also has the "Decades" collections which would be worth a go too.

I've just had a look at Amazon and if you like what you hear above your best buy would almost certainly be the two "Virgin Years" collections. There's "1974-1978" which is a 3 disc set (currently £9.99 inc. delivery lowest price) which covers 5 albums, and "1977-1983" a 5 CD set priced £11.99 at the moment which covers another 7 albums. That works out at less than two quid per album.

Here's a bit of me, covering Tangerine Dream's Force Majeure, one of my favourite tracks...