Assessing movement online

I have been deeeeeep into eBay since losing my beloved vintage Omega, and I have a question about the hunt...

I'm trying to understand how to make a good bet on a movement. Of course I fully expect to get the watch serviced, but, correct if I'm wrong, it seems like some watches are more serviceable than others.

Some sellers give no info about the movement at all. Some sellers will say it's not running and needs a service. Some will say "fully functional" but nothing else. Some will give you qualitative information like "running a little fast but working well."

Some sellers take a picture of the watch on a timegrapher, but a lot of the time readings don't show the watch running perfectly. I am trying to learn which kinds of readings are fatal flaws and which kinds aren't, but I'm wayy amateur here.

And then again, isn't it true that any timegrapher read out is just one snap shot and doesn't really tell you much? Plus they can be rigged? I don't fully understand yet what the timegrapher readings mean in practice.

Some sellers take photos of the movement and the inside of the case. I know you're supposed to check for corrosion and rust, messed up screws, old oil, original and signed parts, serial numbers and of course that the movement is the right one and complete! I have to admit that I haven't trained my eyes to see a lot of this yet.

I'd love to hear any insights you have in reaction to any of this. What do you look for to avoid lemons and money pits? When do you take a risk when minimal information or images are provided?

I’m so sorry this won’t be very helpful but all I can say is buying the seller is the most important thing you can do to protect yourself when buying online - especially one who offers some post purchase support.

I wish I knew of more reliable dealers who sold women's size watches. They are not as good an ROI so I get it. I'm mostly looking at Japanese sellers, who can be hit or miss.