Splurge on the tools to make it comfortable! You'll be spending a lot of time in your home office, so you should make it a place you look forward to being in.
I've invested in a CODE Keyboard, a nice monitor (surprisingly, from a thrift store!), a comfortable Logitech mouse, and pretty sweet JVC HA-NC250 noise-cancelling headphones. I've also been blessed with a solid wood desk from a friend, and a wonderful high-back chair I was given for my birthday a couple of years ago.
I also love physical books, so I have a handy reference section on my desk. I've got a couple of whiteboards, a corkboard, a desk calendar, and this dude for rubber-ducking...
As a result, my workspace is somewhere I legitimately enjoy working.
I listed out the rest of my hardware and software gear here:
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