Looking where and how to start being 17

I’m getting into digital product selling, I found what I want to sell, but I don’t know how. I’m 17 and I don’t have much money, but I’ll be working in the summer. So I want to do something to start making money, because I just be sitting around at home doing nothing, while others make money. And I don’t have the money for courses. I watched a lot of videos around these things even attended couple live streams and other things, but still they don’t explain every thing and tells you to buy course sadly.

I have been researching and looking, reading dozens of reddit posts and so on about digital products, and I understood how to make them, but the main questions are:

Where to sell them, because some people say on already made websites like etsy, amazon etc. and other make their own websites, so which one would you guys recommend to do?

Second question is how do you guys advertise your products, is it worth buying some AI tool to make short form videos around products and then posting them across platforms or there is other ways to advertise?(Maybe you have any AI tool recommendations)

I really wanna do something with my free time instead of wasting my time on games and other stuff.

Where did you guys start and did you buy course or learned everything the hard way?