A skill is the only purchase that goes up in value every time you use it.

Most things you buy start losing value the moment you own them. An ability does the opposite, because every use is also practice, and practice makes the next use better. Nobody can take it, it needs no storage, and it travels with you through every change of job and city.

When you have money or time to spend, look first at what would make you more capable rather than more comfortable. A course, a tool you will learn properly, an hour with someone who knows more. Judge the purchase by what you will be able to do in a year.