Note that there are three tabs/categories at the top:
Hardware: General parts that are needed, most are simple and easy to use.
IC's & Sensors: Components that have data sheets and might require a little more time to fully understand how they work.
Engines, track, etc: A list of some suggested N-scale railway items. HO scale should work as well, but as of Feb, 2023, we've not tested it or heard reports of users successfully testing HO scale.