A screwdriver.

A copy of Sapiens.

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.

I thought this was the dumbest thing until I had one. Now I have one in every toilet.

https://www.amazon.com/16-Color-Activated-Detection-Birthday-Gadgets/dp/B07L2Y84K3

Toilet paper

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

Instructions unclear. Just spent my life savings on all of these great suggestions at once.

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

A shoe horn

A bidet for your bathroom

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

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

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.