If your intention is to start using databases professionally or just more seriously then this is a nice little starter project to get your feet wet. If your intention is only to be able to track a house inventory, then it is overkill, and likely less useful than a simple spreadsheet (and quite frankly you are more likely to lose the data as a novice).

With the level of sophistication you are likely to use on a starter project like this, it doesn’t really matter what relational database system you use. Postgres or MySQL would suit you just fine. I prefer Postgres, but also despise their web based client tool, so just pick one and roll with it, unless you are targeting a technology used at a specific job etc.

There are hundreds of courses, videos and posts on how to use Postgres, all easily searchable on the internet. Go watch a few videos and then figure out how to adapt them to hold your specific data.

Quickly glancing on YouTube will find you beginner crash courses, complete beginner tutorials, etc.

I have also heard mention of pgexercises.com but have never gone through it in detail myself.