Where can I find out about the Argyll & Sutherland Highlanders during the Great War?

[KennethSime]

I always knew my great-great uncle served in WW1 and died in Belgium, but that's about it.

Well, FindMyPast recently made all of their military records free, and I found a record of him quite quickly. His date of death was 09/09/1917, and he's listed as a Private in the 1st/7th Battalion, Princess Louise's Argyll & Sutherland Highlanders.

I wonder if anyone could point me to any resources which might lead to more information about what his battalion may have been doing on or around September 9th. I don't know of any major actions around that time.

I also wonder if there're any resources for knowing some basic stuff like, what were their uniforms like? Did they wear kilts? If so, for daily use or just dress?

Finally, I wonder if there are any more advanced resources one might look to for finding out stuff like when did he enlist, what other actions may he have been apart of, etc.

Thanks in advance for any direction you can provide.