I'm a beginner so take this with a massive grain of salt.
To that end: how do I start?
Look for beginner guides on YouTube. They tell you what needles and yarn to buy, and what stitches to learn first.
I was advised to skip the oversized needles that many videos recommend for the first project.
Learn how to knit in the continental style from the beginning. Watch a few videos on the topic because people hold the tension differently. I tried a few techniques before I found one that felt natural instead of messing me up constantly.
When learning your first stitches, it's better to be too loose than too tight.
I don't want to make a massive investment in case I don't stick with the hobby
You'll be practicing just how to knit and purl for a while, so you just need a pair of straight needles and a ball of yarn, that's like 10-20$ at most, possibly less.
One thing: is it possible to knit machine washable wear?
In my country it's significantly harder to buy natural wool, so I'm guessing you'll have an easy time finding synthetic or superwash wool yarn.