Underwear

A water heater/dispenser, you can find some smaller capacity ones for under 100. I have one that was more than 100 but it's because I love it so much that I wanted a 5 liter one. I can make tea in an instant and always have plenty of near boiling water. They're extremely power efficient so they don't cost much too run.

A good pair of comfortable shoes for your day-to-day circumstances.

Admittedly, this can easily break the $100 limit depending on where you live, your circumstances, etc. but buy the best pair you can afford.

A mug warmer for my coffee and tea cups. No more drinking cold coffee or having to rush through my cup before it gets too cold. It was less than 20 bucks and I use it basically every day. Wonderful purchase

No more stinky boots. Best $40 I've ever spent.

https://www.peetdryer.com/products/original-peet

Pocket reference. It's a tiny book with a ton of potentially useful info.

Hand tools. Wool socks. Fire extinguisher.

Toilet paper

Tide to Go. Less than $10 for a 3-pack and saved my ass whenever my klutz self gets into minor accidents that lead to stained clothes.