The general progression as been:
I need a big flat(ish) surface to build a bike on top of…so build that (the weld table in the pics, looks like metallic swiss cheese).
Need fixtures to hold tubes so the bike is (hopefully) able to be assembled and ridden, so learn how to machine stainless steel, which meant learning how to use a lathe. Go build some fixtures.
Learn how to design a bike. Bikes seem “easy” and “simple”. That’s because over more than 100 years, they’ve been brought to a state of “irreducible complexity”. Not so easy as they look.
I suck at brazing. My left hand literally does not know what my right hand is doing. It’s like balancing an egg atop a drinking straw…