Hamilton Khaki Field Auto - touted and well respected by enthusiasts, but it was a huge miss for me. Busy dial, very reflective glass, poor lume, polished bezel for a field watch, and the H-10 movement doesn’t take well to being manually wound (which I learned the hard way and it took 9 weeks for swatch to warranty).

‘Value’ watches - bought too many because they were a great watch at a great deal. Found myself just churning through them.

Overly ‘fun’ and striking dials - owned a few Zelos pieces that were well made for the price and I was drawn by the striking dials. Great honeymoon period but I eventually got bored and sold them.

Chronographs and GMTs - i kept buying them to check the boxes, but found them too thick, too busy, and/or found myself not using the complication

Tbh, I don’t truly ‘regret’ many purchases as in most cases I was able to sell them and recoup most of my funds, but I do appreciate your eagerness to learn from others’ mistakes. The one thing I’d say is that there’s a ton of value in going in person and trying watches on the wrist. It’s very different than staring at macro photos and scrutinizing spec sheets. You’ll find yourself liking otherwise boring watches (BB58), finding some pieces youd otherwise love not feel quite right (seamaster), and find the exceptions to your previous learnings (I adore the sbga413 Shunbun despite it arguably falling into that fun and striking dial comment above).

Enjoy and best of luck!