All the Bon Scott albums are essential, as is Back in Black and at a push, For Those about to Rock. After that it gets patchy although the Razor’s Edge and Black Ice are pretty good.
Form the beginning, High Voltage and Dirty Deeds are a band finding their feet but knocking out some absolutely fantastic blues-based rock. TNT, the Aus-only album, is a mix of both the above but most of the tracks appear elsewhere.
Let There Be Rock is a proper hard rock album and the closest they got to the ‘heavy metal’ tag sometimes applied to them. It’s nowhere near Sabbath-level metal though and is the first full album with no weak tracks.
Powerage is the high point, for me at least. Different sound to LTBR and a bit more blues comes back, great mix of fantastic tracks.
If You Want Blood…. is one of the top 5 live albums, ever. More energy than you can shake a stick at and they are very tight. Some of the versions on here are the definitives.
Highway to Hell, different sound again. Much more ‘pop’ due to Mutt Lange’s production, but not in a bad way. Great from start to finish.
As mentioned above, if you can get Live from Atlantic Studios from the Bonfire box set, then do it. Considering that it was recorded in front of about 10 people and Bon is clearly hammered, it is truly outstanding. ’74 Jailbreak is the easiest way to get hold of some of the originally Aus-only tracks and is worth it for Angus’ playing on Soul Stripper alone.