I second The Richard D. James Album - I think it’s simply his best full-length record.
Also, the 8-track Come to Daddy EP plays like a perfect “sampler” of Richard’s many styles - from the drill-n-bass electro punk of the title track to pretty piano ambient (“flim”) to the single most jaw-droppingly insane piece of rhythm programming I’ve ever heard (“bucephalus bouncing ball”) and so on. It makes a great introduction to him.
Definitely pick up that Windowlicker single - the title track (and video included on the CD) is life-changing, but the other two tracks are great, too, especially the third one, a really gorgeous little music box piece.