New to eBikes - where to start?

Hey everyone!

Just joined the forum – super excited to dive into the eBike world. I'm completely new to this, and honestly, the idea of a custom build is really appealing, but it also feels a bit overwhelming. For those of you who've gone the custom route, where did you even begin? Did you pick a frame first, then motor/battery, or did you have a specific use case (like commuting 20 miles daily on mixed terrain) that dictated your component choices? Any advice for a newbie trying to figure out the best starting point for a DIY build would be awesome!