A lot of bands have great debut albums. Obviously this list is just a fraction of all the great debut albums out there, but it's a start. I'll keep expanding this list continuously, so all suggestions are welcome. All the albums here are ranked according to genre and then alphabetically. If a certain album belongs to the (in your opinion) wrong genre, then definitely let me know.
When searching albums of a certain genre, just press "Ctrl + F" and then enter the genre you're looking for. For example, when looking for death metal albums, simply enter "[death]" after you pressed "Ctrl + F" and you'll be at the right place in no time, so it works perfectly.
LeKiwi and mz also gave a ton of suggestions of which I still have to check most albums out.
I have new suggestions for you =p. Not sure if I haven't suggested them before:
For you avantgarde section:
Dog Fashion Disco
Also, it seems that you are, like me, a sludge noob. I like these bands (listened to some of these just last week for the first time):
Also, Flourishing is really good sludge tech death.
Battle Of Mice
And P.H.O.B.O.S of course =p