Ahh, the joys of primary source records!

I can only partially parse them myself - there's a lot of shorthand and abbreviations as you can probably tell - but the basic picture is that your relative spent most of his wartime service in the 3rd Australian Divisional Ammunition Column (the "3rd DAC" which shows up throughout that), with what looks like a transfer at some point to the divisional artillery directly. He received a couple of promotions, being discharged as a sergeant, so he did reasonably well for himself.

His civilian trade in the attestation paper is listed as a farrier. It comes up in the course of his service, and he's referred to a few times as a "Far.Sgt." or farrier sergeant, so he likely spent most of his service taking care of the horses in the units he was attached to. (This was a big deal for First World War artillery units, which spent a lot of their time hauling enormous amounts of ammunition around in pretty nasty environments.)

He was stationed in France from November 1916 onward, which likely placed him in the thick of most of the major engagements the 3rd Australian Division was involved with in the second half of the war. Some of these - this isn't a comprehensive list - included Messines (early June 1917), Broodseinde (October), and Amiens during the Hundred Days Offensive of the following summer.

Casualty forms in the records suggest that something happened to him - wounded, injured, fell ill, etc. - but I can't parse anything specific there, and there aren't any lengthy gaps in his record aside from a mention of a couple weeks' leave in England (which could have simply been that - leave, not recuperation). Someone more familiar with Australian records might be able to chip in.

He remained in Europe for several months after the armistice, either on continued duty in France or as one of the hundreds of thousands of soldiers not-so-patiently waiting their turn to be discharged and return home. His number finally came up in the summer of 1919, when he got a spot on the ship Prinz Ludwig, a German passenger ship given to the Allies as part of war reparations and tasked with ferrying ANZAC personnel back home.

As a personal note, I'm a little envious - I'm waiting on my great-grandfather's records from the Canadian Expeditionary Force, which is in a stack of six hundred thousand files being gradually digitized by surname. He's up in the S crowd and they're currently on N...