The band has a massive discography and I really want to start in the right direction with this band, so what release of theirs should I start with?

I say start with Winterschatten based on the reviews.

After that, expand to the well-reviewed full lengths, then the not-so-well-reviewed full lengths, then from there any EPs and Demos. Go one album at a time.

Other than that, I have no clue where to start with this band... but if I wanted to start with them I'd go with Winterschatten and expand to the full lengths, going from there.

There are some bands I'll listen to even the early demos of, but many I have just one full length out of a long discography and I haven't bothered to check out their other stuff.

Nowhere. Ain't worth your time and effort. You're better off listening to Burzum, because Vinterriket is just a mediocre Burzum clone.

I did not listen to a lot of releases from Vinterriket, but I would recommend to start with Der letzte Winter - Der Ewigkeit entgegen, this is the first one I got and it worked fine for me.

Also, I would recommend you to check Horizontmelancholie for something a bit different, the use of accoustic guitars here turned out to be something refreshing for Vinterriket and it was very effective for me.

His ambient stuff does in my opinion not have many things in common with Burzum. His earlier Black Metal stuff was more influenced my Limbonic Art and the likes.

I suggest the early Black Metal stuff, and ignore the ambient things. "Stürme Der Letzten Stille" tape would be a good start.

I always thought that was an interesting idea, but the plastic drum machine utterly destroyed it for me. Everytime I start to get into it, here comes the warp speed doublebass one would normally expect to be put through to by the likes of Chainsaw Dissection. His black metal ventures haven't really struck a chord with me, though they've certainly gotten better on more recent efforts like Gebirgshöhenstille.

Though I will say he pulled it off pretty well in Das Winterreich, the split of which with Paysage d'Hiver (who is far better) is probably his best release.

A good starting point would be ...Und Die Nacht Kam Schweren, his first full length and the first to start to sound somewhat professional after the long smattering of demos and splits. But there's practically zero progression today from then, and any of his other albums are as good as any other as far as I'm concerned; even that album starts to sound repetitious halfway through. The bonus track ...Und Donner Durchflutete Die Täler is pretty good though.