All the tools I had back then were a cordless drill, two hand saws, some chisels and a sander. You don't need much and you should only buy new equipment if the project requires it. Also I did not "design" anything, just did some sketches on paper then improvised on the spot.
Woodworking instantly became my hobby and after watching some Youtube videos - including ALL of Paul Sellers videos - I made a decision to go the unplugged route.
If I were to start over I'd read a book about the basic principles of woodworking and joinery, especially how the wood behaves and how to apprloach it. I sort of got all of this by intuition, however an introductory book would be a better start. Also I should have mastered sharpening way earlier in my journey.