One of the most important things is to get good, low blue-light, task lighting for your desk.
At the top end is a Dyson Lightcycle that I cannot live without, but any LED height/angle adjustable lamp is better than shadows over your desk.
When I say I cannot live without the Dyson, I am hooked on it matching the outdoor light and looking after my circadian rhythms so I can get a better night’s sleep.
Most workplaces are air-conditioned at a constant 23°. Air conditioning at home is at your cost and can be expensive – remember if you claim that cost it comes up as wages that you pay tax on.
As we are now in Autumn a fan/heater may suffice and if you have more cash a combo air purifier is better. And yes you can salary sacrifice that too!
My wife and I are frequent remote workers and have NBN 100/40Mbps. It is not that we need the top speed, but when the internet is congested (as it increasingly is at present), our speeds are still reasonable.
Remote workers need upload speed more than download, especially if they are working on a remote server or using Microsoft Teams or similar. At a minimum upgrade to 50/20Mbps.
Why? You are more likely to use video conferencing, a secure VPN and need more remote speed.
If you suffer from ADSL or poor internet speeds, there are 4G alternatives like the D-Link 4G LTE router that may give you better speeds but TRY IT FIRST as poor 4G signals mean even poorer speed.
A 24-27″ 1920×1080 (FHD) monitor is fine for office use. Most PC/Mac/Laptops will have HDMI port or dongle to support that.
If desk space is an issue the Samsung Space 27 or 32″ fold flat monitor is ideal but don’t forget that you can also buy monitor arms that do the same.
If you need dual monitors, look for small side bezels and use two of the same (or you will go crazy with different fonts and colours). You will generally need a dock, and these will run two FHD easily – only a Thunderbolt 3 dock and computer will run dual 4K. Docks connect via USB-A 3.0 (blue insert), USB-C 3.1 Gen 1 (5Gbps), USB-C 3.1/2 Gen 2 (10Gbps) and Thunderbolt 3 (20 to 40Gbps). Obviously, the faster you go, the more expensive it gets.
Or if dual monitors are not possible you can get a 38, 42 or larger curved 1080p monitor that only needs one HDMI port.
You do not need a 4K monitor (with 100% Adobe RCG) unless you are a designer, videographer, CAD engineer or photo editor. Then you need a Thunderbolt 3 PC and dock to drive them.
Also, look at your desk space and make sure you have at least 60cm distance between your monitor and eyes.
Again, it is best to get what your office uses. But before you get locked into one or the other ecosystem (PC or Mac) look at the software that you use first.
If you only use Microsoft Office 365, and a browser, then the cheapest PC does all that. So, an Intel Core i3, 4/128GB, Windows 10 device will do that with aplomb. These start from about $400.