How would I go about making an item stock system using HttpService?

I had an idea of making a limited item stock with serial IDs similar to Roblox’s LimitedU items. After doing a bit of research I have figured I need to use HttpService to get a value from an external website (Possibly Netlify) which would then increase after a player has purchased said item. I have no past experience or knowledge of JavaScript, so keep that in mind.

Any help would be appreciated as I’ve been stuck on this for a while now.

The documentation for HttpService is pretty good for examples, it should point you in the right direction

Yeah read through that, but I’m struggling with making a data counter on a third party website which will track the stock of an item.

You will want to make it so the game can send a get request to the endpoint to retrieve a json dictionary of the serial ID’s then you can send a post request to update the dictionary setting the serial ID to the user ID to establish ownership.
I would personally create my own API for this, you can find many tutorials for this on youtube etc.

Anything I should be searching on youtube in particular?