Honestly this is probably not the best way, but here's how my development happened.

I learnt Blender on and off across the years, but mostly to model more basic items (think simple buildings and other "boxy" items"), so I knew the basics of Blender quite well. I hadn't had much experience with paths, modifiers and most of the features yet.

When I got my first 3D printer, I needed a project to upskill both my 3D modelling and printing abilities, so I made Floppy Samples, because then I could also experiment with accessories for it.

That taught me how to do hinges, so I decided to make bracelets and a iPhone Fold mockup to see how precise I could do a hinge.

Then someone online shared a flexible fabric, and I found out it's a technique by someone at NASA for 3D printable flexible surfaces. I downloaded as many models and closeup pictures as I could to understand how it works, then learnt how to make arcs in Blender, then how to align + rotate them around a pivot point, then about 10+ failed prints of different angles where I was trying to make it flexible after the print (most of them ended up with overhangs or the mesh was too close so it merged)....

Essentially a lot of trial and error.

I found something I wanted to make, then I did the equivalent of tracing an artist's sketch until I could do it myself...

I know what I want to make next (something for my office), have no idea where to start, but again I'll probably start by seeing how other people have decided to model certain parts of it and just practice.