Where to look for watches to learn repairing on

honestly just search for lots of "untested" or "parts only" seikos on ebay and hope for the best...

Look for anything vintage with a Seiko 6309 or a manual wind ST19 movement. They are relatively simple to tear down and you can find tons of spare parts or cheap donor movements online if you accidentally snap a click spring.

Look for Elgin or Waltham pocket watches on eBay. They have larger components that are easier to handle than my smaller Farer or Baltic pieces, and the parts are everywhere if you break something. Value-wise, you can usually snag a bag of non-runners for under fifty bucks to practice on.

Stick to old pocket watches or simple hand-wound ETA 2824 clones. You want a movement with decent bridge layout and visible finishing so you can actually see where the pivots seat without losing your mind.

Look for 1960s or 70s hand-wound pieces from dead brands with an AS or ETA movement. Stay far away from chronographs or anything with a date complication until you can move a hairspring without sweating.

I wouldn't start with vintage pieces because hidden rust and brittle parts can be a nightmare for a beginner. It's usually better to buy a few cheap Seiko clones or San Martin models with NH35 movements so you can learn on something modern and standardized first.

Go for a used Vostok Amphibia or Komandirskie from eBay. They're tank-like and cheap enough that it won't hurt when you inevitably lose a part.